High 7.5Published Oct 8, 2026

CVE-2026-78660HTTP/2 transport accepts malformed framing-related headers in net/http

Updated under an hour ago (2026-10-19 11:10 UTC)

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It affects Go standard library net/http and 2 other products. Add what you run to find out whether that includes you.

EPSS puts the chance of exploitation in the next 30 days at 0.30%, higher than 22% of scored CVEs.

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Every CVE for Go standard library net/http

Exploited in the last 30 days

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.

CVSS: 7.5 HIGH (v3.1, CISA ADP)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weakness (CWE): CWE-444
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): 0.30% (percentile 22)
Assigned by: Go
NVD analysis: Awaiting Analysis
Record last updated: Oct 9, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Go standard library net/http go_standard_library:net_http (from the name)	before 1.26.9	CNA record
Go standard library net/http/internal/http2 go_standard_library:net_http_internal_http2 (from the name)	from 1.27.0-0 before 1.27.2	CNA record
golang.org/x/net golang.org/x/net/http2 golang.org_x_net:http2 (from the name)	before 0.60.0	CNA record

References

https://go.dev/cl/835145
https://go.dev/cl/836385
https://go.dev/issue/81115
https://groups.google.com/g/golang-announce/c/U2fTuyDJznI
https://pkg.go.dev/vuln/GO-2026-6610

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.