Versions of Express.js prior to 4.19.2 and pre-release alpha and beta versions before 5.0.0-beta.3 are affected by an open redirect vulnerability using malformed URLs.
When a user of Express performs a redirect using a user-provided URL Express performs an encode using encodeurl on the contents before passing it to the location header. This can cause malformed URLs to be evaluated in unexpected ways by common redirect allow list implementations in Express applications, leading to an Open Redirect via bypass of a properly implemented allow list.
The main method impacted is res.location() but this is also called from within res.redirect().
An initial fix went out with express@4.19.0, we then patched a feature regression in 4.19.1 and added improved handling for the bypass in 4.19.2.
Workarounds
The fix for this involves pre-parsing the url string with either require('node:url').parse or new URL. These are steps you can take on your own before passing the user input string to res.location or res.redirect.
This PR contains the following updates:
4.19.1->4.19.2GitHub Vulnerability Alerts
CVE-2024-29041
Impact
Versions of Express.js prior to 4.19.2 and pre-release alpha and beta versions before 5.0.0-beta.3 are affected by an open redirect vulnerability using malformed URLs.
When a user of Express performs a redirect using a user-provided URL Express performs an encode using
encodeurlon the contents before passing it to thelocationheader. This can cause malformed URLs to be evaluated in unexpected ways by common redirect allow list implementations in Express applications, leading to an Open Redirect via bypass of a properly implemented allow list.The main method impacted is
res.location()but this is also called from withinres.redirect().Patches
https://github.com/expressjs/express/commit/0867302ddbde0e9463d0564fea5861feb708c2dd https://github.com/expressjs/express/commit/0b746953c4bd8e377123527db11f9cd866e39f94
An initial fix went out with
express@4.19.0, we then patched a feature regression in4.19.1and added improved handling for the bypass in4.19.2.Workarounds
The fix for this involves pre-parsing the url string with either
require('node:url').parseornew URL. These are steps you can take on your own before passing the user input string tores.locationorres.redirect.References
https://github.com/expressjs/express/pull/5539 https://github.com/koajs/koa/issues/1800 https://expressjs.com/en/4x/api.html#res.location
Release Notes
expressjs/express (express)
### [`v4.19.2`](https://togithub.com/expressjs/express/blob/HEAD/History.md#4192--2024-03-25) [Compare Source](https://togithub.com/expressjs/express/compare/4.19.1...4.19.2) \========== - Improved fix for open redirect allow list bypassConfiguration
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