{"id":"CVE-2026-78660","sourceIdentifier":"security@golang.org","published":"2026-10-08T23:17:03.510","lastModified":"2026-10-09T17:16:49.243","vulnStatus":"Awaiting Analysis","cveTags":[],"descriptions":[{"lang":"en","value":"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."}],"affected":[{"source":"security@golang.org","affectedData":[{"vendor":"Go standard library","product":"net/http","defaultStatus":"unaffected","collectionURL":"https://pkg.go.dev","packageName":"net/http","programRoutines":[{"name":"http2clientConnReadLoop.handleResponse"},{"name":"Client.CloseIdleConnections"},{"name":"Client.Do"},{"name":"Client.Get"},{"name":"Client.Head"},{"name":"Client.Post"},{"name":"Client.PostForm"},{"name":"ClientConn.Close"},{"name":"ClientConn.RoundTrip"},{"name":"Get"},{"name":"Head"},{"name":"Post"},{"name":"PostForm"},{"name":"Transport.CloseIdleConnections"},{"name":"Transport.NewClientConn"},{"name":"Transport.RoundTrip"},{"name":"http1ClientConn.Close"},{"name":"http1ClientConn.RoundTrip"},{"name":"http2Transport.NewClientConn"},{"name":"http2Transport.RoundTrip"},{"name":"http2Transport.RoundTripOpt"},{"name":"http2clientConnPool.GetClientConn"},{"name":"http2noDialClientConnPool.GetClientConn"},{"name":"http2noDialH2RoundTripper.NewClientConn"},{"name":"http2noDialH2RoundTripper.RoundTrip"},{"name":"http2unencryptedTransport.RoundTrip"}],"versions":[{"version":"0","lessThan":"1.26.9","versionType":"semver","status":"affected"}]},{"vendor":"Go standard library","product":"net/http/internal/http2","defaultStatus":"unaffected","collectionURL":"https://pkg.go.dev","packageName":"net/http/internal/http2","programRoutines":[{"name":"clientConnReadLoop.handleResponse"},{"name":"Transport.AddConn"},{"name":"Transport.NewClientConn"},{"name":"Transport.RoundTrip"},{"name":"Transport.RoundTripOpt"},{"name":"clientConnPool.GetClientConn"},{"name":"noDialClientConnPool.GetClientConn"}],"versions":[{"version":"1.27.0-0","lessThan":"1.27.2","versionType":"semver","status":"affected"}]},{"vendor":"golang.org/x/net","product":"golang.org/x/net/http2","defaultStatus":"unaffected","collectionURL":"https://pkg.go.dev","packageName":"golang.org/x/net/http2","programRoutines":[{"name":"clientConnReadLoop.handleResponse"},{"name":"Transport.NewClientConn"},{"name":"Transport.RoundTrip"},{"name":"Transport.RoundTripOpt"},{"name":"clientConnPool.GetClientConn"},{"name":"noDialClientConnPool.GetClientConn"},{"name":"noDialH2RoundTripper.NewClientConn"},{"name":"noDialH2RoundTripper.RoundTrip"},{"name":"unencryptedTransport.RoundTrip"}],"versions":[{"version":"0","lessThan":"0.60.0","versionType":"semver","status":"affected"}]}]}],"metrics":{"cvssMetricV31":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","baseScore":7.5,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"HIGH","availabilityImpact":"NONE"},"exploitabilityScore":3.9,"impactScore":3.6}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-10-09T16:21:51.217328Z","id":"CVE-2026-78660","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"weaknesses":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","type":"Secondary","description":[{"lang":"en","value":"CWE-444"}]}],"references":[{"url":"https://go.dev/cl/835145","source":"security@golang.org"},{"url":"https://go.dev/cl/836385","source":"security@golang.org"},{"url":"https://go.dev/issue/81115","source":"security@golang.org"},{"url":"https://groups.google.com/g/golang-announce/c/U2fTuyDJznI","source":"security@golang.org"},{"url":"https://pkg.go.dev/vuln/GO-2026-6610","source":"security@golang.org"}]}