MailKit crashes from headers in Korean

[SviatoslavRazmyslov]

Describe the bug

I received an email from Korean student and saw a MailKit exception in my service.

Platform:

• OS: Linux
• .NET Runtime: .NET 8
• MailKit Version: 4.7.1.1
• MimeKit Version: 4.7.1

Exception

System.FormatException: Failed to parse headers.
   at MimeKit.MimeParser.ParseHeaders(Byte* inbuf, CancellationToken cancellationToken)
   at MimeKit.MimeParser.ParseHeaders(CancellationToken cancellationToken)
   at MimeKit.HeaderList.Load(ParserOptions options, Stream stream, CancellationToken cancellationToken)
   at MimeKit.HeaderList.Load(Stream stream, CancellationToken cancellationToken)
   at MimeKit.MessageDispositionNotification.get_Fields()

To Reproduce Steps to reproduce the behavior:

I guess the reason is this:

From: "=?UTF-8?B?7ZmN7KeE6re8?=" <jkhong@bu.ac.kr>

or that:

Reporting-UA: mail.bu.ac.kr; 백석대학교

Expected behavior

A mail is loaded without exceptions.

[jstedfast]

It's neither of those. Any chance you can send me the message privately? I need to see the full content of the message/disposition-notification MIME part.

The content is malformed somehow.

[jstedfast]

Moving this to MimeKit since, if it is a bug, then it's a bug in my MimeKit library and not MailKit.

[SviatoslavRazmyslov]

Hi @jstedfast,

I've attached the original .eml file of the Korean mail.

Read- PVS-Studio for educational purposes.txt

[jstedfast]

Okay, so, looking at this email, the reason that it failed wasn't because it was in Korean but was because the Content-Transfer-Encoding is set to base64, therefore, when it goes to parse the content (another set of "headers"), it fails because the parser is dealing with the result of whatever the base64 decoder gives back (which will be garbage because it's not really base64 encoded).

I'm not sure what can really be done by MimeKit, here. This is really a bug in the sending client.

[SviatoslavRazmyslov]

@jstedfast , thank you for the feedback!