{"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":"high","cvss":7.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-405","CWE-770"],"vendor":"stdlib","product":"stdlib","affected":["stdlib < 1.26.9","stdlib >= 1.27.0-0, < 1.27.2","golang.org/x/net < 0.60.0"],"patched":["stdlib 1.26.9","stdlib 1.27.2","golang.org/x/net 0.60.0"],"published":"2026-10-08","updated":"2026-10-09","sourceUpdated":"2026-10-09T16:35:35.900","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"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-78659.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-78659"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2548339"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-78659"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-78659"},{"url":"https://access.redhat.com/errata/RHSA-2026:87040"},{"url":"https://access.redhat.com/errata/RHSA-2026:86093"},{"url":"https://access.redhat.com/errata/RHSA-2026:86203"},{"url":"https://access.redhat.com/errata/RHSA-2026:87246"},{"url":"https://access.redhat.com/errata/RHSA-2026:87041"},{"url":"https://access.redhat.com/errata/RHSA-2026:87042"},{"url":"https://access.redhat.com/errata/RHSA-2026:87043"},{"url":"https://access.redhat.com/errata/RHSA-2026:86196"},{"url":"https://access.redhat.com/errata/RHSA-2026:87245"}],"tags":["nvd","osv","go","cve.org","csaf","vex","red-hat"],"aliases":["GO-2026-6603","BIT-golang-2026-78659"],"ecosystem":"go","ingestedAt":"2026-10-09T00:19:50.975Z","epss":0.00627,"epssPercentile":0.49861,"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"partial","timestamp":"2026-10-09T15:27:33.510545Z"},"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.\n\n## Package advisory (CVE-2026-78659)\n\nAffected packages:\n\n- `stdlib < 1.26.9`\n- `stdlib >= 1.27.0-0, < 1.27.2`\n- `golang.org/x/net < 0.60.0`\n\nPatched in:\n\n- `stdlib 1.26.9`\n- `stdlib 1.27.2`\n- `golang.org/x/net 0.60.0`\n\nSource: https://osv.dev/vulnerability/GO-2026-6603\n\n## Vendor advisories\n\n- **RHSA-2026:87040** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream EUS (v. 10.0) · released 2026-10-21 · [advisory](https://access.redhat.com/errata/RHSA-2026:87040)\n- **RHSA-2026:86093** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 10) · released 2026-10-20 · [advisory](https://access.redhat.com/errata/RHSA-2026:86093)\n- **RHSA-2026:86203** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 8) · released 2026-10-20 · [advisory](https://access.redhat.com/errata/RHSA-2026:86203)\n- **RHSA-2026:87246** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream AUS (v.8.6), Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6) · released 2026-10-21 · [advisory](https://access.redhat.com/errata/RHSA-2026:87246)\n- **RHSA-2026:87041** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream E4S (v.9.2) · released 2026-10-21 · [advisory](https://access.redhat.com/errata/RHSA-2026:87041)\n- **RHSA-2026:87042** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream E4S (v.9.4) · released 2026-10-21 · [advisory](https://access.redhat.com/errata/RHSA-2026:87042)\n- **RHSA-2026:87043** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream EUS (v.9.6) · released 2026-10-21 · [advisory](https://access.redhat.com/errata/RHSA-2026:87043)\n- **RHSA-2026:86196** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9) · released 2026-10-20 · [advisory](https://access.redhat.com/errata/RHSA-2026:86196)\n- **Red Hat VEX** · Moderate · affected: OpenShift Developer Tools and Services, OpenShift Pipelines, OpenShift Serverless, OpenShift Service Mesh 3, Red Hat Ansible Automation Platform 2, Red Hat Ceph Storage 7, … · no fix planned: OpenShift Developer Tools and Services, Red Hat Ansible Automation Platform 2, Red Hat OpenStack Platform 16.2, Red Hat OpenStack Platform 17.1, … · updated 2026-10-23 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-78659.json)\n- **RHSA-2026:87245** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream E4S (v.8.8), Red Hat Enterprise Linux AppStream TUS (v.8.8) · released 2026-10-21 · [advisory](https://access.redhat.com/errata/RHSA-2026:87245)","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[{"seq":218564,"id":"CVE-2026-78659","ts":1791565564928,"field":"cvss","old":null,"new":"7.5"},{"seq":218563,"id":"CVE-2026-78659","ts":1791565564928,"field":"severity","old":"none","new":"high"}]}