{"id":"CVE-2026-26308","aliases":["BIT-envoy-2026-26308","GHSA-ghc4-35x6-crw5"],"url":"https://o3.security/vulnerability/CVE-2026-26308","summary":"Envoy has an RBAC Header Validation Bypass via Multi-Value Header Concatenation","details":"Envoy is a high-performance edge/middle/service proxy. Prior to 1.37.1, 1.36.5, 1.35.8, and 1.34.13, the Envoy RBAC (Role-Based Access Control) filter contains a logic vulnerability in how it validates HTTP headers when multiple values are present for the same header name. Instead of validating each header value individually, Envoy concatenates all values into a single comma-separated string. This behavior allows attackers to bypass RBAC policies—specifically \"Deny\" rules—by sending duplicate headers, effectively obscuring the malicious value from exact-match mechanisms. This vulnerability is fixed in 1.37.1, 1.36.5, 1.35.8, and 1.34.13.","published":"2026-03-10T19:01:28.062Z","modified":"2026-08-07T21:09:03.723329Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/envoyproxy/envoy","fixedVersion":"1.37.1"},{"ecosystem":"Go","name":"github.com/envoyproxy/envoy","fixedVersion":"1.36.5"},{"ecosystem":"Go","name":"github.com/envoyproxy/envoy","fixedVersion":"1.35.9"},{"ecosystem":"Go","name":"github.com/envoyproxy/envoy","fixedVersion":"1.34.13"}],"fix":{"url":"https://github.com/envoyproxy/envoy/commit/b6ba0b2294b98484fb0ed8556897d1073cc27867","label":"envoyproxy/envoy@b6ba0b2"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/26xxx/CVE-2026-26308.json"},{"type":"ADVISORY","url":"https://github.com/envoyproxy/envoy/security/advisories/GHSA-ghc4-35x6-crw5"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-26308"},{"type":"FIX","url":"https://github.com/envoyproxy/envoy/commit/b6ba0b2294b98484fb0ed8556897d1073cc27867"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-07T21:09:03.723329Z"}}