HTTP 2/3: treat messages containing connection-specific header fields malformed#66669
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DeagleGross merged 4 commits intoMay 15, 2026
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Pull request overview
Updates Kestrel’s HTTP/2 and HTTP/3 request header validation to fully enforce RFC 9113 §8.2.2 and RFC 9114 §4.2 by treating messages that include connection-specific header fields as malformed (beyond just connection and invalid te).
Changes:
- Expanded HTTP/2 and HTTP/3 connection-specific header detection to include
transfer-encoding,keep-alive,proxy-connection, andupgrade(while keeping thete: trailersexception). - Added functional tests for HTTP/2 and HTTP/3 to validate the new connection-specific header rejection behavior.
Show a summary per file
| File | Description |
|---|---|
| src/Servers/Kestrel/test/InMemory.FunctionalTests/Http3/Http3StreamTests.cs | Adds theory coverage ensuring HTTP/3 rejects additional connection-specific request headers. |
| src/Servers/Kestrel/test/InMemory.FunctionalTests/Http2/Http2ConnectionTests.cs | Adds theory coverage ensuring HTTP/2 rejects additional connection-specific request headers. |
| src/Servers/Kestrel/Core/src/Internal/Http3/Http3Stream.cs | Extends connection-specific header detection per RFC 9114 §4.2. |
| src/Servers/Kestrel/Core/src/Internal/Http2/Http2Connection.cs | Extends connection-specific header detection per RFC 9113 §8.2.2. |
Copilot's findings
- Files reviewed: 4/4 changed files
- Comments generated: 0
rokonec
approved these changes
May 13, 2026
This was referenced Jun 4, 2026
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Per RFC 9113 §8.2.2 (HTTP/2) and RFC 9114 §4.2 (HTTP/3), endpoints must treat any message containing connection-specific header fields as malformed. Kestrel's
IsConnectionSpecificHeaderFieldin bothHttp2ConnectionandHttp3Streamonly checked forConnectionandTE, missing the other four headers called out by the RFCs.