{"id":"CVE-2026-78659","title":"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","summary":"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 HTT…","severity":"none","published":"2026-10-08","updated":"2026-10-08","sourceUpdated":"2026-10-08T23:17:03.270","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-78659","references":[{"url":"https://go.dev/cl/847185","label":"security@golang.org"},{"url":"https://go.dev/cl/847314","label":"security@golang.org"},{"url":"https://go.dev/issue/81857","label":"security@golang.org"},{"url":"https://groups.google.com/g/golang-announce/c/U2fTuyDJznI","label":"security@golang.org"},{"url":"https://groups.google.com/g/golang-announce/c/ZPwCyRUuGBs","label":"security@golang.org"},{"url":"https://pkg.go.dev/vuln/GO-2026-6603","label":"security@golang.org"}],"tags":["nvd"],"ingestedAt":"2026-10-09T00:19:50.975Z","slug":"CVE-2026-78659","body":"## Overview\n\nWhen \"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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}