{"id":"CVE-2026-56853","sourceIdentifier":"security@golang.org","published":"2026-08-13T22:17:22.093","lastModified":"2026-09-03T16:37:52.170","vulnStatus":"Awaiting Analysis","cveTags":[],"descriptions":[{"lang":"en","value":"When a server is configured to support unencrypted HTTP/2, it reads a few bytes from each new connection to see if they contain the HTTP/2 client preface. ReadHeaderTimeout is unexpectedly not being applied when doing this."}],"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":"conn.readRequest"},{"name":"conn.serve"},{"name":"ListenAndServe"},{"name":"ListenAndServeTLS"},{"name":"Serve"},{"name":"ServeTLS"},{"name":"Server.ListenAndServe"},{"name":"Server.ListenAndServeTLS"},{"name":"Server.Serve"},{"name":"Server.ServeTLS"}],"versions":[{"version":"0","lessThan":"1.25.13","versionType":"semver","status":"affected"},{"version":"1.26.0-0","lessThan":"1.26.6","versionType":"semver","status":"affected"},{"version":"1.27.0-0","lessThan":"1.27.0-rc.3","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:N/A:H","baseScore":7.5,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"HIGH"},"exploitabilityScore":3.9,"impactScore":3.6}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-08-14T15:22:45.475320Z","id":"CVE-2026-56853","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-770"}]}],"references":[{"url":"https://go.dev/cl/795540","source":"security@golang.org"},{"url":"https://go.dev/issue/80205","source":"security@golang.org"},{"url":"https://groups.google.com/g/golang-announce/c/94pEornpRlI","source":"security@golang.org"},{"url":"https://pkg.go.dev/vuln/GO-2026-6089","source":"security@golang.org"}]}