{"id":"GO-2026-6603","aliases":["BIT-golang-2026-78659","CVE-2026-78659"],"title":"HTTP/2 server memory exhaustion due to Trailer headers in net/http","titleSource":"OSV","descriptionSource":"OSV","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.","severity":"unknown","score":null,"published":"2026-10-08T22:31:09.000Z","modified":"2026-11-14T13:12:13.462Z","withdrawn":false,"knownExploited":false,"affected":[{"ecosystem":"Go","name":"stdlib","sources":[{"name":"OSV · GO-2026-6603","url":"https://osv.dev/vulnerability/GO-2026-6603"}],"ranges":[{"events":[{"introduced":"0"},{"fixed":"1.26.9"}],"type":"SEMVER"}],"versions":[],"fixed":["1.26.9"]},{"ecosystem":"Go","name":"stdlib","sources":[{"name":"OSV · GO-2026-6603","url":"https://osv.dev/vulnerability/GO-2026-6603"}],"ranges":[{"events":[{"introduced":"1.27.0-0"},{"fixed":"1.27.2"}],"type":"SEMVER"}],"versions":[],"fixed":["1.27.2"]},{"ecosystem":"Go","name":"golang.org/x/net","sources":[{"name":"OSV · GO-2026-6603","url":"https://osv.dev/vulnerability/GO-2026-6603"}],"ranges":[{"events":[{"introduced":"0"},{"fixed":"0.60.0"}],"type":"SEMVER"}],"versions":[],"fixed":["0.60.0"]}],"sourceAffected":[],"references":["https://go.dev/cl/847185","https://go.dev/cl/847314","https://go.dev/issue/81857","https://groups.google.com/g/golang-announce/c/U2fTuyDJznI","https://groups.google.com/g/golang-announce/c/ZPwCyRUuGBs"],"sources":[{"name":"OSV","id":"GO-2026-6603","modified":"2026-11-14T13:12:13.462737073Z","url":"https://osv.dev/vulnerability/GO-2026-6603"}],"assessments":[],"products":[],"remediation":[],"observedAt":"2026-11-14T15:05:01.939Z","kev":{"status":"not-listed","checkedAt":"2026-11-15T03:55:35.117Z"},"coverage":[{"source":"NVD","status":"refresh-failed","attemptedAt":"2026-11-14T00:45:33.165Z"},{"source":"GHSA","status":"no-result","checkedAt":"2026-11-14T00:35:36.150Z","attemptedAt":"2026-11-14T00:35:36.150Z"},{"source":"EUVD","status":"available","checkedAt":"2026-11-14T00:35:38.492Z","attemptedAt":"2026-11-14T00:35:38.492Z"},{"source":"EPSS","status":"available","checkedAt":"2026-11-14T00:35:35.126Z","attemptedAt":"2026-11-14T00:35:35.126Z"}],"evidence":[{"source":"FIRST EPSS","id":"CVE-2026-78659","url":"https://www.first.org/epss/","probability":0.00866,"percentile":0.59221,"date":"2026-11-13","checkedAt":"2026-11-14T00:35:35.126Z"},{"source":"ENISA EUVD","id":"EUVD-2026-95419","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-95419","modified":"Oct 9, 2026, 3:34:24 PM","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","checkedAt":"2026-11-14T00:35:38.492Z"}],"aiSummary":null}