{"cve":"CVE-2026-26308","nvd":{"published":"2026-03-10T20:16:35.707","modified":"2026-06-17T10:26:03.823","status":"Analyzed","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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N","score":8.2},"cwes":["CWE-863"],"references":["https://github.com/envoyproxy/envoy/commit/b6ba0b2294b98484fb0ed8556897d1073cc27867","https://github.com/envoyproxy/envoy/security/advisories/GHSA-ghc4-35x6-crw5"],"products":["envoyproxy:envoy"],"source":"nvd","synced_at":"2026-10-19T22:25:53.701907451+00:00"},"epss":{"cve":"CVE-2026-26308","score":0.00305,"percentile":0.23311,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-ghc4-35x6-crw5","url":"https://osv.dev/vulnerability/GHSA-ghc4-35x6-crw5","summary":"Envoy has RBAC Header Validation Bypass via Multi-Value Header Concatenation","modified":"2026-04-13T17:46:32.629556Z","packages":[{"ecosystem":"Go","name":"github.com/envoyproxy/envoy","purl":"pkg:golang/github.com/envoyproxy/envoy","ranges":[">=1.37.0 <1.37.1"],"fixed":["1.37.1"]},{"ecosystem":"Go","name":"github.com/envoyproxy/envoy","purl":"pkg:golang/github.com/envoyproxy/envoy","ranges":[">=1.36.0 <1.36.5"],"fixed":["1.36.5"]},{"ecosystem":"Go","name":"github.com/envoyproxy/envoy","purl":"pkg:golang/github.com/envoyproxy/envoy","ranges":[">=1.35.0 <1.35.9"],"fixed":["1.35.9"]},{"ecosystem":"Go","name":"github.com/envoyproxy/envoy","purl":"pkg:golang/github.com/envoyproxy/envoy","ranges":["<1.34.13"],"fixed":["1.34.13"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}