The _encode_invalid_chars function in util/url.py in the urllib3 library 1.25.2 through 1.25.7 for Python allows a denial of service (CPU consumption) because of an inefficient algorithm. The percent_encodings array contains all matches of percent encodings. It is not deduplicated. For a URL of length N, the size of percent_encodings may be up to O(N). The next step (normalize existing percent-encoded bytes) also takes up to O(N) for each step, so the total time is O(N^2). If percent_encodings were deduplicated, the time to compute _encode_invalid_chars would be O(kN), where k is at most 484 ((10+6*2)^2).
urllib3 before 1.25.9 allows CRLF injection if the attacker controls the HTTP request method, as demonstrated by inserting CR and LF control characters in the first argument of putrequest(). NOTE: this is similar to CVE-2020-26116.
urllib3 doesn't treat the Cookie HTTP header special or provide any helpers for managing cookies over HTTP, that is the responsibility of the user. However, it is possible for a user to specify a Cookie header and unknowingly leak information via HTTP redirects to a different origin if that user doesn't disable redirects explicitly.
Users must handle redirects themselves instead of relying on urllib3's automatic redirects to achieve safe processing of the Cookie header, thus we decided to strip the header by default in order to further protect users who aren't using the correct approach.
Affected usages
We believe the number of usages affected by this advisory is low. It requires all of the following to be true to be exploited:
Using an affected version of urllib3 (patched in v1.26.17 and v2.0.6)
Using the Cookie header on requests, which is mostly typical for impersonating a browser.
Not disabling HTTP redirects
Either not using HTTPS or for the origin server to redirect to a malicious origin.
Remediation
Upgrading to at least urllib3 v1.26.17 or v2.0.6
Disabling HTTP redirects using redirects=False when sending requests.
urllib3 previously wouldn't remove the HTTP request body when an HTTP redirect response using status 303 "See Other" after the request had its method changed from one that could accept a request body (like POST) to GET as is required by HTTP RFCs. Although the behavior of removing the request body is not specified in the section for redirects, it can be inferred by piecing together information from different sections and we have observed the behavior in other major HTTP client implementations like curl and web browsers.
A client SHOULD NOT generate content in a GET request unless it is made directly to an origin server that has previously indicated, in or out of band, that such a request has a purpose and will be adequately supported.
Affected usages
Because the vulnerability requires a previously trusted service to become compromised in order to have an impact on confidentiality we believe the exploitability of this vulnerability is low. Additionally, many users aren't putting sensitive data in HTTP request bodies, if this is the case then this vulnerability isn't exploitable.
Both of the following conditions must be true to be affected by this vulnerability:
If you're using urllib3 and submitting sensitive information in the HTTP request body (such as form data or JSON)
The origin service is compromised and starts redirecting using 303 to a malicious peer or the redirected-to service becomes compromised.
Remediation
You can remediate this vulnerability with any of the following steps:
Upgrade to a patched version of urllib3 (v1.26.18 or v2.0.7)
Disable redirects for services that you aren't expecting to respond with redirects with redirects=False.
Disable automatic redirects with redirects=False and handle 303 redirects manually by stripping the HTTP request body.
When using urllib3's proxy support with ProxyManager, the Proxy-Authorization header is only sent to the configured proxy, as expected.
However, when sending HTTP requests without using urllib3's proxy support, it's possible to accidentally configure the Proxy-Authorization header even though it won't have any effect as the request is not using a forwarding proxy or a tunneling proxy. In those cases, urllib3 doesn't treat the Proxy-Authorization HTTP header as one carrying authentication material and thus doesn't strip the header on cross-origin redirects.
Because this is a highly unlikely scenario, we believe the severity of this vulnerability is low for almost all users. Out of an abundance of caution urllib3 will automatically strip the Proxy-Authorization header during cross-origin redirects to avoid the small chance that users are doing this on accident.
Users should use urllib3's proxy support or disable automatic redirects to achieve safe processing of the Proxy-Authorization header, but we still decided to strip the header by default in order to further protect users who aren't using the correct approach.
Affected usages
We believe the number of usages affected by this advisory is low. It requires all of the following to be true to be exploited:
Setting the Proxy-Authorization header without using urllib3's built-in proxy support.
Not disabling HTTP redirects.
Either not using an HTTPS origin server or for the proxy or target origin to redirect to a malicious origin.
Remediation
Using the Proxy-Authorization header with urllib3's ProxyManager.
Disabling HTTP redirects using redirects=False when sending requests.
In the urllib3 library through 1.24.2 for Python, CRLF injection is possible if the attacker controls the request parameter.
Release Notes
urllib3/urllib3 (urllib3)
### [`v1.26.19`](https://togithub.com/urllib3/urllib3/compare/1.26.18...1.26.19)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.26.18...1.26.19)
### [`v1.26.18`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#12618-2023-10-17)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.26.17...1.26.18)
\====================
- Made body stripped from HTTP requests changing the request method to GET after HTTP 303 "See Other" redirect responses.
### [`v1.26.17`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#12617-2023-10-02)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.26.16...1.26.17)
\====================
- Added the `Cookie` header to the list of headers to strip from requests when redirecting to a different host. As before, different headers can be set via `Retry.remove_headers_on_redirect`. (`#3139 `\_)
### [`v1.26.16`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#12616-2023-05-23)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.26.15...1.26.16)
\====================
- Fixed thread-safety issue where accessing a `PoolManager` with many distinct origins
would cause connection pools to be closed while requests are in progress (`#2954 `\_)
### [`v1.26.15`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#12615-2023-03-10)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.26.14...1.26.15)
\====================
- Fix socket timeout value when `HTTPConnection` is reused (`#2645 `\__)
- Remove "!" character from the unreserved characters in IPv6 Zone ID parsing
(`#2899 `\__)
- Fix IDNA handling of '\x80' byte (`#2901 `\__)
### [`v1.26.14`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#12614-2023-01-11)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.26.13...1.26.14)
\====================
- Fixed parsing of port 0 (zero) returning None, instead of 0. (`#2850 `\__)
- Removed deprecated getheaders() calls in contrib module. Fixed the type hint of `PoolKey.key_retries` by adding `bool` to the union. (`#2865 `\__)
### [`v1.26.13`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#12613-2022-11-23)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.26.12...1.26.13)
\====================
- Deprecated the `HTTPResponse.getheaders()` and `HTTPResponse.getheader()` methods.
- Fixed an issue where parsing a URL with leading zeroes in the port would be rejected
even when the port number after removing the zeroes was valid.
- Fixed a deprecation warning when using cryptography v39.0.0.
- Removed the `<4` in the `Requires-Python` packaging metadata field.
### [`v1.26.12`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#12612-2022-08-22)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.26.11...1.26.12)
\====================
- Deprecated the `urllib3[secure]` extra and the `urllib3.contrib.pyopenssl` module.
Both will be removed in v2.x. See this `GitHub issue `\_
for justification and info on how to migrate.
### [`v1.26.11`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#12611-2022-07-25)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.26.10...1.26.11)
\====================
- Fixed an issue where reading more than 2 GiB in a call to `HTTPResponse.read` would
raise an `OverflowError` on Python 3.9 and earlier.
### [`v1.26.10`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#12610-2022-07-07)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.26.9...1.26.10)
\====================
- Removed support for Python 3.5
- Fixed an issue where a `ProxyError` recommending configuring the proxy as HTTP
instead of HTTPS could appear even when an HTTPS proxy wasn't configured.
### [`v1.26.9`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#1269-2022-03-16)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.26.8...1.26.9)
\===================
- Changed `urllib3[brotli]` extra to favor installing Brotli libraries that are still
receiving updates like `brotli` and `brotlicffi` instead of `brotlipy`.
This change does not impact behavior of urllib3, only which dependencies are installed.
- Fixed a socket leaking when `HTTPSConnection.connect()` raises an exception.
- Fixed `server_hostname` being forwarded from `PoolManager` to `HTTPConnectionPool`
when requesting an HTTP URL. Should only be forwarded when requesting an HTTPS URL.
### [`v1.26.8`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#1268-2022-01-07)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.26.7...1.26.8)
\===================
- Added extra message to `urllib3.exceptions.ProxyError` when urllib3 detects that
a proxy is configured to use HTTPS but the proxy itself appears to only use HTTP.
- Added a mention of the size of the connection pool when discarding a connection due to the pool being full.
- Added explicit support for Python 3.11.
- Deprecated the `Retry.MAX_BACKOFF` class property in favor of `Retry.DEFAULT_MAX_BACKOFF`
to better match the rest of the default parameter names. `Retry.MAX_BACKOFF` is removed in v2.0.
- Changed location of the vendored `ssl.match_hostname` function from `urllib3.packages.ssl_match_hostname`
to `urllib3.util.ssl_match_hostname` to ensure Python 3.10+ compatibility after being repackaged
by downstream distributors.
- Fixed absolute imports, all imports are now relative.
### [`v1.26.7`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#1267-2021-09-22)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.26.6...1.26.7)
\===================
- Fixed a bug with HTTPS hostname verification involving IP addresses and lack
of SNI. (Issue [#2400](https://togithub.com/urllib3/urllib3/issues/2400))
- Fixed a bug where IPv6 braces weren't stripped during certificate hostname
matching. (Issue [#2240](https://togithub.com/urllib3/urllib3/issues/2240))
### [`v1.26.6`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#1266-2021-06-25)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.26.5...1.26.6)
\===================
- Deprecated the `urllib3.contrib.ntlmpool` module. urllib3 is not able to support
it properly due to `reasons listed in this issue `\_.
If you are a user of this module please leave a comment.
- Changed `HTTPConnection.request_chunked()` to not erroneously emit multiple
`Transfer-Encoding` headers in the case that one is already specified.
- Fixed typo in deprecation message to recommend `Retry.DEFAULT_ALLOWED_METHODS`.
### [`v1.26.5`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#1265-2021-05-26)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.26.4...1.26.5)
\===================
- Fixed deprecation warnings emitted in Python 3.10.
- Updated vendored `six` library to 1.16.0.
- Improved performance of URL parser when splitting
the authority component.
### [`v1.26.4`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#1264-2021-03-15)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.26.3...1.26.4)
\===================
- Changed behavior of the default `SSLContext` when connecting to HTTPS proxy
during HTTPS requests. The default `SSLContext` now sets `check_hostname=True`.
### [`v1.26.3`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#1263-2021-01-26)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.26.2...1.26.3)
\===================
- Fixed bytes and string comparison issue with headers (Pull [#2141](https://togithub.com/urllib3/urllib3/issues/2141))
- Changed `ProxySchemeUnknown` error message to be
more actionable if the user supplies a proxy URL without
a scheme. (Pull [#2107](https://togithub.com/urllib3/urllib3/issues/2107))
### [`v1.26.2`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#1262-2020-11-12)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.26.1...1.26.2)
\===================
- Fixed an issue where `wrap_socket` and `CERT_REQUIRED` wouldn't
be imported properly on Python 2.7.8 and earlier (Pull [#2052](https://togithub.com/urllib3/urllib3/issues/2052))
### [`v1.26.1`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#12616-2023-05-23)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.26.0...1.26.1)
\====================
- Fixed thread-safety issue where accessing a `PoolManager` with many distinct origins
would cause connection pools to be closed while requests are in progress (`#2954 `\_)
### [`v1.26.0`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#1260-2020-11-10)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.25.11...1.26.0)
\===================
- **NOTE: urllib3 v2.0 will drop support for Python 2**.
`Read more in the v2.0 Roadmap `\_.
- Added support for HTTPS proxies contacting HTTPS servers (Pull [#1923](https://togithub.com/urllib3/urllib3/issues/1923), Pull [#1806](https://togithub.com/urllib3/urllib3/issues/1806))
- Deprecated negotiating TLSv1 and TLSv1.1 by default. Users that
still wish to use TLS earlier than 1.2 without a deprecation warning
should opt-in explicitly by setting `ssl_version=ssl.PROTOCOL_TLSv1_1` (Pull [#2002](https://togithub.com/urllib3/urllib3/issues/2002))
**Starting in urllib3 v2.0: Connections that receive a `DeprecationWarning` will fail**
- Deprecated `Retry` options `Retry.DEFAULT_METHOD_WHITELIST`, `Retry.DEFAULT_REDIRECT_HEADERS_BLACKLIST`
and `Retry(method_whitelist=...)` in favor of `Retry.DEFAULT_ALLOWED_METHODS`,
`Retry.DEFAULT_REMOVE_HEADERS_ON_REDIRECT`, and `Retry(allowed_methods=...)`
(Pull [#2000](https://togithub.com/urllib3/urllib3/issues/2000)) **Starting in urllib3 v2.0: Deprecated options will be removed**
- Added default `User-Agent` header to every request (Pull [#1750](https://togithub.com/urllib3/urllib3/issues/1750))
- Added `urllib3.util.SKIP_HEADER` for skipping `User-Agent`, `Accept-Encoding`,
and `Host` headers from being automatically emitted with requests (Pull [#2018](https://togithub.com/urllib3/urllib3/issues/2018))
- Collapse `transfer-encoding: chunked` request data and framing into
the same `socket.send()` call (Pull [#1906](https://togithub.com/urllib3/urllib3/issues/1906))
- Send `http/1.1` ALPN identifier with every TLS handshake by default (Pull [#1894](https://togithub.com/urllib3/urllib3/issues/1894))
- Properly terminate SecureTransport connections when CA verification fails (Pull [#1977](https://togithub.com/urllib3/urllib3/issues/1977))
- Don't emit an `SNIMissingWarning` when passing `server_hostname=None`
to SecureTransport (Pull [#1903](https://togithub.com/urllib3/urllib3/issues/1903))
- Disabled requesting TLSv1.2 session tickets as they weren't being used by urllib3 (Pull [#1970](https://togithub.com/urllib3/urllib3/issues/1970))
- Suppress `BrokenPipeError` when writing request body after the server
has closed the socket (Pull [#1524](https://togithub.com/urllib3/urllib3/issues/1524))
- Wrap `ssl.SSLError` that can be raised from reading a socket (e.g. "bad MAC")
into an `urllib3.exceptions.SSLError` (Pull [#1939](https://togithub.com/urllib3/urllib3/issues/1939))
### [`v1.25.11`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#12511-2020-10-19)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.25.10...1.25.11)
\====================
- Fix retry backoff time parsed from `Retry-After` header when given
in the HTTP date format. The HTTP date was parsed as the local timezone
rather than accounting for the timezone in the HTTP date (typically
UTC) (Pull [#1932](https://togithub.com/urllib3/urllib3/issues/1932), Pull [#1935](https://togithub.com/urllib3/urllib3/issues/1935), Pull [#1938](https://togithub.com/urllib3/urllib3/issues/1938), Pull [#1949](https://togithub.com/urllib3/urllib3/issues/1949))
- Fix issue where an error would be raised when the `SSLKEYLOGFILE`
environment variable was set to the empty string. Now `SSLContext.keylog_file`
is not set in this situation (Pull [#2016](https://togithub.com/urllib3/urllib3/issues/2016))
### [`v1.25.10`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#12510-2020-07-22)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.25.9...1.25.10)
\====================
- Added support for `SSLKEYLOGFILE` environment variable for
logging TLS session keys with use with programs like
Wireshark for decrypting captured web traffic (Pull [#1867](https://togithub.com/urllib3/urllib3/issues/1867))
- Fixed loading of SecureTransport libraries on macOS Big Sur
due to the new dynamic linker cache (Pull [#1905](https://togithub.com/urllib3/urllib3/issues/1905))
- Collapse chunked request bodies data and framing into one
call to `send()` to reduce the number of TCP packets by 2-4x (Pull [#1906](https://togithub.com/urllib3/urllib3/issues/1906))
- Don't insert `None` into `ConnectionPool` if the pool
was empty when requesting a connection (Pull [#1866](https://togithub.com/urllib3/urllib3/issues/1866))
- Avoid `hasattr` call in `BrotliDecoder.decompress()` (Pull [#1858](https://togithub.com/urllib3/urllib3/issues/1858))
### [`v1.25.9`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#1259-2020-04-16)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.25.8...1.25.9)
\===================
- Added `InvalidProxyConfigurationWarning` which is raised when
erroneously specifying an HTTPS proxy URL. urllib3 doesn't currently
support connecting to HTTPS proxies but will soon be able to
and we would like users to migrate properly without much breakage.
See `this GitHub issue `\_
for more information on how to fix your proxy config. (Pull [#1851](https://togithub.com/urllib3/urllib3/issues/1851))
- Drain connection after `PoolManager` redirect (Pull [#1817](https://togithub.com/urllib3/urllib3/issues/1817))
- Ensure `load_verify_locations` raises `SSLError` for all backends (Pull [#1812](https://togithub.com/urllib3/urllib3/issues/1812))
- Rename `VerifiedHTTPSConnection` to `HTTPSConnection` (Pull [#1805](https://togithub.com/urllib3/urllib3/issues/1805))
- Allow the CA certificate data to be passed as a string (Pull [#1804](https://togithub.com/urllib3/urllib3/issues/1804))
- Raise `ValueError` if method contains control characters (Pull [#1800](https://togithub.com/urllib3/urllib3/issues/1800))
- Add `__repr__` to `Timeout` (Pull [#1795](https://togithub.com/urllib3/urllib3/issues/1795))
### [`v1.25.8`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#1258-2020-01-20)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.25.7...1.25.8)
\===================
- Drop support for EOL Python 3.4 (Pull [#1774](https://togithub.com/urllib3/urllib3/issues/1774))
- Optimize \_encode_invalid_chars (Pull [#1787](https://togithub.com/urllib3/urllib3/issues/1787))
### [`v1.25.7`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#1257-2019-11-11)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.25.6...1.25.7)
\===================
- Preserve `chunked` parameter on retries (Pull [#1715](https://togithub.com/urllib3/urllib3/issues/1715), Pull [#1734](https://togithub.com/urllib3/urllib3/issues/1734))
- Allow unset `SERVER_SOFTWARE` in App Engine (Pull [#1704](https://togithub.com/urllib3/urllib3/issues/1704), Issue [#1470](https://togithub.com/urllib3/urllib3/issues/1470))
- Fix issue where URL fragment was sent within the request target. (Pull [#1732](https://togithub.com/urllib3/urllib3/issues/1732))
- Fix issue where an empty query section in a URL would fail to parse. (Pull [#1732](https://togithub.com/urllib3/urllib3/issues/1732))
- Remove TLS 1.3 support in SecureTransport due to Apple removing support (Pull [#1703](https://togithub.com/urllib3/urllib3/issues/1703))
### [`v1.25.6`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#1256-2019-09-24)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.25.5...1.25.6)
\===================
- Fix issue where tilde (`~`) characters were incorrectly
percent-encoded in the path. (Pull [#1692](https://togithub.com/urllib3/urllib3/issues/1692))
### [`v1.25.5`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#1255-2019-09-19)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.25.4...1.25.5)
\===================
- Add mitigation for BPO-37428 affecting Python <3.7.4 and OpenSSL 1.1.1+ which
caused certificate verification to be enabled when using `cert_reqs=CERT_NONE`.
(Issue [#1682](https://togithub.com/urllib3/urllib3/issues/1682))
### [`v1.25.4`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#1254-2019-09-19)
[Compare Source](https://togithub.com/urllib3/urllib3/compare/1.25.3...1.25.4)
\===================
- Propagate Retry-After header settings to subsequent retries. (Pull [#1607](https://togithub.com/urllib3/urllib3/issues/1607))
- Fix edge case where Retry-After header was still respected even when
explicitly opted out of. (Pull [#1607](https://togithub.com/urllib3/urllib3/issues/1607))
- Remove dependency on `rfc3986` for URL parsing.
- Fix issue where URLs containing invalid characters within `Url.auth` would
raise an exception instead of percent-encoding those characters.
- Add support for `HTTPResponse.auto_close = False` which makes HTTP responses
work well with BufferedReaders and other `io` module features. (Pull [#1652](https://togithub.com/urllib3/urllib3/issues/1652))
- Percent-encode invalid characters in URL for `HTTPConnectionPool.request()` (Pull [#1673](https://togithub.com/urllib3/urllib3/issues/1673))
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This PR contains the following updates:
==1.25.3->==1.26.19==1.24.2->==1.26.19GitHub Vulnerability Alerts
CVE-2020-7212
The _encode_invalid_chars function in util/url.py in the urllib3 library 1.25.2 through 1.25.7 for Python allows a denial of service (CPU consumption) because of an inefficient algorithm. The percent_encodings array contains all matches of percent encodings. It is not deduplicated. For a URL of length N, the size of percent_encodings may be up to O(N). The next step (normalize existing percent-encoded bytes) also takes up to O(N) for each step, so the total time is O(N^2). If percent_encodings were deduplicated, the time to compute _encode_invalid_chars would be O(kN), where k is at most 484 ((10+6*2)^2).
CVE-2020-26137
urllib3 before 1.25.9 allows CRLF injection if the attacker controls the HTTP request method, as demonstrated by inserting CR and LF control characters in the first argument of
putrequest(). NOTE: this is similar to CVE-2020-26116.CVE-2023-43804
urllib3 doesn't treat the
CookieHTTP header special or provide any helpers for managing cookies over HTTP, that is the responsibility of the user. However, it is possible for a user to specify aCookieheader and unknowingly leak information via HTTP redirects to a different origin if that user doesn't disable redirects explicitly.Users must handle redirects themselves instead of relying on urllib3's automatic redirects to achieve safe processing of the
Cookieheader, thus we decided to strip the header by default in order to further protect users who aren't using the correct approach.Affected usages
We believe the number of usages affected by this advisory is low. It requires all of the following to be true to be exploited:
Cookieheader on requests, which is mostly typical for impersonating a browser.Remediation
redirects=Falsewhen sending requests.Cookieheader.CVE-2023-45803
urllib3 previously wouldn't remove the HTTP request body when an HTTP redirect response using status 303 "See Other" after the request had its method changed from one that could accept a request body (like
POST) toGETas is required by HTTP RFCs. Although the behavior of removing the request body is not specified in the section for redirects, it can be inferred by piecing together information from different sections and we have observed the behavior in other major HTTP client implementations like curl and web browsers.From RFC 9110 Section 9.3.1:
Affected usages
Because the vulnerability requires a previously trusted service to become compromised in order to have an impact on confidentiality we believe the exploitability of this vulnerability is low. Additionally, many users aren't putting sensitive data in HTTP request bodies, if this is the case then this vulnerability isn't exploitable.
Both of the following conditions must be true to be affected by this vulnerability:
Remediation
You can remediate this vulnerability with any of the following steps:
redirects=False.redirects=Falseand handle 303 redirects manually by stripping the HTTP request body.CVE-2024-37891
When using urllib3's proxy support with
ProxyManager, theProxy-Authorizationheader is only sent to the configured proxy, as expected.However, when sending HTTP requests without using urllib3's proxy support, it's possible to accidentally configure the
Proxy-Authorizationheader even though it won't have any effect as the request is not using a forwarding proxy or a tunneling proxy. In those cases, urllib3 doesn't treat theProxy-AuthorizationHTTP header as one carrying authentication material and thus doesn't strip the header on cross-origin redirects.Because this is a highly unlikely scenario, we believe the severity of this vulnerability is low for almost all users. Out of an abundance of caution urllib3 will automatically strip the
Proxy-Authorizationheader during cross-origin redirects to avoid the small chance that users are doing this on accident.Users should use urllib3's proxy support or disable automatic redirects to achieve safe processing of the
Proxy-Authorizationheader, but we still decided to strip the header by default in order to further protect users who aren't using the correct approach.Affected usages
We believe the number of usages affected by this advisory is low. It requires all of the following to be true to be exploited:
Proxy-Authorizationheader without using urllib3's built-in proxy support.Remediation
Proxy-Authorizationheader with urllib3'sProxyManager.redirects=Falsewhen sending requests.Proxy-Authorizationheader.CVE-2019-11236
In the urllib3 library through 1.24.2 for Python, CRLF injection is possible if the attacker controls the request parameter.
Release Notes
urllib3/urllib3 (urllib3)
### [`v1.26.19`](https://togithub.com/urllib3/urllib3/compare/1.26.18...1.26.19) [Compare Source](https://togithub.com/urllib3/urllib3/compare/1.26.18...1.26.19) ### [`v1.26.18`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#12618-2023-10-17) [Compare Source](https://togithub.com/urllib3/urllib3/compare/1.26.17...1.26.18) \==================== - Made body stripped from HTTP requests changing the request method to GET after HTTP 303 "See Other" redirect responses. ### [`v1.26.17`](https://togithub.com/urllib3/urllib3/blob/HEAD/CHANGES.rst#12617-2023-10-02) [Compare Source](https://togithub.com/urllib3/urllib3/compare/1.26.16...1.26.17) \==================== - Added the `Cookie` header to the list of headers to strip from requests when redirecting to a different host. As before, different headers can be set via `Retry.remove_headers_on_redirect`. (`#3139Configuration
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