CVE-2026-78663

critical · 9.1

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.

9.1

CVSS

0.6%

EPSS (exploit prob.)

49th

EPSS percentile

2026-10-08

Published

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

Weaknesses

CWE-675

References

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

Query this programmatically:

curl https://evil-db.io/api/v1/cve/CVE-2026-78663