{"id":"CVE-2026-78659","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-78659","generatedAt":"2026-10-28T01:01:10.606Z","title":"For HTTP/2 servers, a malicious client can exploit this by sending a \"Trailer\" header that declares a large number of fields, causing the server to allocate a disproportionate amount of memory while bypassing Server.MaxHeaderValueCount and…","description":"When \"Trailer\" headers are sent by a client, the HTTP server internally uses the header values to populate the Request.Trailer map passed to the server handler. Because Request.Trailer is a map, each entry incurs memory overhead. For HTTP/2 servers, a malicious client can exploit this by sending a \"Trailer\" header that declares a large number of fields, causing the server to allocate a disproportionate amount of memory while bypassing Server.MaxHeaderValueCount and Server.MaxHeaderBytes limits. This exploit is not applicable for HTTP/1 servers, which do not support multiplexing a large number of requests over one TCP connection, and whose Server.MaxHeaderBytes are calculated differently.","published":"2026-10-08T23:17:03.000Z","lastModified":"2026-10-09T16:35:36.000Z","status":"Awaiting Analysis","sourceIdentifier":"security@golang.org","cvss":{"version":"3.1","score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"cwe":["CWE-405"],"affected":[],"epss":{"score":0.00627,"percentile":0.49785,"date":"2026-10-26","history":[{"date":"2026-10-09","score":0.00227,"percentile":0.12359}]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.63%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[{"kind":"scored","label":"Newly scored","at":"2026-10-09T17:00:08.000Z","detail":{"from":null,"score":"7.5","severity":"HIGH","fromSeverity":null},"summary":"Now scored CVSS 7.5 HIGH."},{"kind":"new","label":"New CVE","at":"2026-10-08T23:17:03.000Z","detail":{"score":null,"severity":null,"publishedAt":"2026-10-08T23:17:03.270Z"},"summary":"New CVE, high severity (CVSS 7.5)."}],"references":[{"url":"https://go.dev/cl/847185","source":"security@golang.org"},{"url":"https://go.dev/cl/847314","source":"security@golang.org"},{"url":"https://go.dev/issue/81857","source":"security@golang.org"},{"url":"https://groups.google.com/g/golang-announce/c/U2fTuyDJznI","source":"security@golang.org"},{"url":"https://groups.google.com/g/golang-announce/c/ZPwCyRUuGBs","source":"security@golang.org"},{"url":"https://pkg.go.dev/vuln/GO-2026-6603","source":"security@golang.org"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-78659","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}