net/http: apply header timeout to server's unencrypted HTTP/2 check

When a server is configured to support unencrypted HTTP/2,
it reads a few bytes from each new connection to see if they
contain the HTTP/2 client preface. This read was being done
with no timeout applied. Apply the header timeout (since this
is essentially reading the first headers from the connection).

Hoist the header timeout into the server serve loop so we can
use a single timeout to cover both the HTTP/2 preface and
the first HTTP/1 headers.

Thanks to Vsevolod Naumov and Ainar Garipov from AdGuard for reporting this issue.

Fixes #80205
Fixes CVE-2026-56853

Change-Id: I69943a79453967bc2f70da5b5ceeac936a6a6964
Reviewed-on: https://go-review.googlesource.com/c/go/+/795540
Reviewed-by: Nicholas Husin <nsh@golang.org>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Nicholas Husin <husin@google.com>
Auto-Submit: Damien Neil <dneil@google.com>
2 files changed
tree: 6ea581969a0456f63ee7a217e843e92196afa85c
  1. .github/
  2. api/
  3. doc/
  4. lib/
  5. misc/
  6. src/
  7. test/
  8. .gitattributes
  9. .gitignore
  10. codereview.cfg
  11. CONTRIBUTING.md
  12. go.env
  13. LICENSE
  14. PATENTS
  15. README.md
  16. SECURITY.md
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