CVE-2026-78660CWE-444

CVE-2026-78660

High · published October 9, 2026

CVSS v3.1
7.5
EPSS
0%
Percentile
21.8
In the wild
Unconfirmed
What it is

Historically, we have been rather lax about malformed framing-related headers in our HTTP/2 implementation, as they cannot interfere with HTTP/2 framing. However, this makes it possible for our HTTP/2 implementation to forward responses containing such headers to an HTTP/1 client when acting as a reverse proxy. If the HTTP/1 client also does not behave strictly enough, this can result in response smuggling.

The record
Technical detail
CVSS v3.1
7.5 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
CVSS v4.0
Not supplied
EPSS
0.00303 · 21.8th percentile
Weakness
CWE-444 · Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Published
2026-10-09T03:17Z
References (5)
https://go.dev/cl/835145 · [email protected]https://go.dev/cl/836385 · [email protected]https://go.dev/issue/81115 · [email protected]https://groups.google.com/g/golang-announce/c/U2fTuyDJznI · [email protected]https://pkg.go.dev/vuln/GO-2026-6610 · [email protected]
EPSS history
Timeline
  • 10 OCT 03:31Z
    EPSS moved — → 0%
    epss
  • 08 OCT 22:53Z
    HTTP/2 transport accepts malformed framing-related headers in net/http
    cvelistv5
  • 08 OCT 22:53Z
    HTTP/2 transport accepts malformed framing-related headers in net/http
    cvelistv5