{"id":"CVE-2026-26308","state":"PUBLISHED","title":"Envoy has an RBAC Header Validation Bypass via Multi-Value Header Concatenation","description":"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.","publishedAt":"2026-03-10T19:01:28.062Z","updatedAt":"2026-03-10T20:12:40.604Z","severity":{"score":7.5,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["envoyproxy envoy"],"affected":[{"vendor":"envoyproxy","product":"envoy","versions":[{"version":">= 1.37.0, < 1.37.1","status":"affected"},{"version":">= 1.36.0, < 1.36.5","status":"affected"},{"version":">= 1.35.0, < 1.35.9","status":"affected"},{"version":"< 1.34.13","status":"affected"}]}],"references":["https://github.com/envoyproxy/envoy/security/advisories/GHSA-ghc4-35x6-crw5","https://github.com/envoyproxy/envoy/commit/b6ba0b2294b98484fb0ed8556897d1073cc27867"],"weaknesses":["CWE-863"],"ingestedAt":"2026-10-29T20:11:21.040Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/26xxx/CVE-2026-26308.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-26308","state":"PUBLISHED","datePublished":"2026-03-10T19:01:28.062Z","dateUpdated":"2026-03-10T20:12:40.604Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-02-13T16:27:51.804Z"},"containers":{"cna":{"title":"Envoy has an RBAC Header Validation Bypass via Multi-Value Header Concatenation","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"envoyproxy","product":"envoy","versions":[{"version":">= 1.37.0, < 1.37.1","status":"affected"},{"version":">= 1.36.0, < 1.36.5","status":"affected"},{"version":">= 1.35.0, < 1.35.9","status":"affected"},{"version":"< 1.34.13","status":"affected"}]}],"references":[{"url":"https://github.com/envoyproxy/envoy/security/advisories/GHSA-ghc4-35x6-crw5","name":"https://github.com/envoyproxy/envoy/security/advisories/GHSA-ghc4-35x6-crw5","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/envoyproxy/envoy/commit/b6ba0b2294b98484fb0ed8556897d1073cc27867","name":"https://github.com/envoyproxy/envoy/commit/b6ba0b2294b98484fb0ed8556897d1073cc27867","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":7.5,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"LOW","privilegesRequired":"NONE","scope":"CHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-863","lang":"en","description":"CWE-863: Incorrect Authorization","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-03-10T19:01:28.062Z"},"source":{"advisory":"GHSA-ghc4-35x6-crw5","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-26308","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2026-03-10T20:10:29.907912Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-03-10T20:12:40.604Z"}}]}}}