{"id":"CVE-2026-78663","title":"The HTTP/2 server can refund connection-level flow control twice for the same data: Once when a client resets a stream (refunding data for any sent-but-unread portion of the stream), and again when a request handler reads the buffered da…","summary":"The HTTP/2 server can refund connection-level flow control twice for the same data: Once when a client resets a stream (refunding data for any sent-but-unread portion of the stream), and again when a request handler reads the buffered da…","severity":"critical","cvss":9.1,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H","cwe":["CWE-675","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":"2026-10-09T17:16:49.420","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-78663","references":[{"url":"https://go.dev/cl/847187","label":"security@golang.org"},{"url":"https://go.dev/cl/847310","label":"security@golang.org"},{"url":"https://go.dev/issue/81743","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-2026-6612","label":"security@golang.org"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-78663.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-78663"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2548345"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-78663"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-78663"},{"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","csaf","vex","red-hat","cve.org","score-dispute"],"epss":0.00622,"epssPercentile":0.49589,"aliases":["GO-2026-6612","BIT-golang-2026-78663"],"ecosystem":"go","scores":{"nvd":9.1,"vendor":5.3,"adp":9.1},"ingestedAt":"2026-10-09T00:19:50.975Z","ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"total","timestamp":"2026-10-09T16:40:08.220862Z"},"slug":"CVE-2026-78663","body":"## Overview\n\nThe HTTP/2 server can refund connection-level flow control twice for the same data: Once when a client resets a stream (refunding data for any sent-but-unread portion of the stream), and again when a request handler reads the buffered data. A malicious client can exploit this to bypass the configured connection-level flow control limit (MaxReceiveBufferPerConnection). Total buffered data is still limited by the concurrent stream limit and stream-level flow control.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Package advisory (CVE-2026-78663)\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-2026-6612\n\n## Vendor advisories\n\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-2026-78663.json)\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- **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":"midnight","depthScore":50,"depthScoreParts":{"impact":50.1,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[{"seq":218576,"id":"CVE-2026-78663","ts":1791569311909,"field":"cvss","old":"5.3","new":"9.1"},{"seq":218575,"id":"CVE-2026-78663","ts":1791569311909,"field":"severity","old":"medium","new":"critical"},{"seq":218468,"id":"CVE-2026-78663","ts":1791533891330,"field":"cvss","old":null,"new":"5.3"},{"seq":218467,"id":"CVE-2026-78663","ts":1791533891330,"field":"severity","old":"none","new":"medium"}]}