Vulnerability in Go standard library net/http

[ Why it matters ]Priority signals

• Critical severity: CVSS 9.1

[ Description ]Official description

The HTTP/2 server can refund connection-level flow control twice for the same data: Once when a client resets a stream (refunding data for any sent-but-unread portion of the stream), and again when a request handler reads the buffered data. A malicious client can exploit this to bypass the configured connection-level flow control limit (MaxReceiveBufferPerConnection). Total buffered data is still limited by the concurrent stream limit and stream-level flow control.

[ Fixes ]Fixes and patches

No fix or interim patch is linked from our sources yet. Check the vendor references below and limit exposure of affected systems until a fix is available.

[ Advisories ]Government CERT advisories

• BSI CERT-Bund8 Oct 2026WID-SEC-2026-3841

  Golang Go: Multiple vulnerabilities Translated from German

  Risk mediumCVE-2026-94439CVE-2026-56866CVE-2026-94447+12 more CVEs

[ References ]References

• go.dev/cl/847187
• go.dev/cl/847310
• go.dev/issue/81743
• groups.google.com/g/golang-announce/c/U2fTuyDJznI
• groups.google.com/g/golang-announce/c/ZPwCyRUuGBs
• pkg.go.dev/vuln/GO-2026-6612