{"id":"CVE-2026-47778","state":"PUBLISHED","title":"Envoy: Embedded NUL in TLS DNS SAN Truncation in the Default TLS Certificate Validator. (Auth Bypass)","description":"Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.35.11, 1.36.7, 1.37.3, and 1.38.1, a structural flaw was identified in DefaultCertValidator::verifySubjectAltName where the extracted DNS SAN string is cast to a C-style string using .c_str() before being passed to the Utility::dnsNameMatch() algorithm. If the attacker serves a certificate with a dNSName SAN containing an embedded NUL byte, the helper Utility::generalNameAsString captures the complete string including the NUL. However, when .c_str() evaluates it, implicit conversion to absl::string_view inside dnsNameMatch relies on strlen(), prematurely truncating the evaluation context. Envoy evaluates trucated string against the exact required config_san match and returns true, thereby successfully validating the string with the Nul byte for an upstream routing. This vulnerability is fixed in 1.35.11, 1.36.7, 1.37.3, and 1.38.1.","publishedAt":"2026-06-26T17:27:57.707Z","updatedAt":"2026-06-27T02:53:13.826Z","severity":{"score":4.4,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["envoyproxy envoy"],"affected":[{"vendor":"envoyproxy","product":"envoy","versions":[{"version":">= 1.38.0, < 1.38.1","status":"affected"},{"version":">= 1.37.0, < 1.37.3","status":"affected"},{"version":">= 1.36.0, < 1.36.7","status":"affected"},{"version":"< 1.35.11","status":"affected"}]}],"references":["https://github.com/envoyproxy/envoy/security/advisories/GHSA-f8x4-rw5x-f3r7"],"weaknesses":["CWE-158"],"ingestedAt":"2026-10-29T20:12:07.131Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/47xxx/CVE-2026-47778.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-47778","state":"PUBLISHED","datePublished":"2026-06-26T17:27:57.707Z","dateUpdated":"2026-06-27T02:53:13.826Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-05-19T22:36:16.883Z"},"containers":{"cna":{"title":"Envoy: Embedded NUL in TLS DNS SAN Truncation in the Default TLS Certificate Validator. (Auth Bypass)","descriptions":[{"lang":"en","value":"Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.35.11, 1.36.7, 1.37.3, and 1.38.1, a structural flaw was identified in DefaultCertValidator::verifySubjectAltName where the extracted DNS SAN string is cast to a C-style string using .c_str() before being passed to the Utility::dnsNameMatch() algorithm. If the attacker serves a certificate with a dNSName SAN containing an embedded NUL byte, the helper Utility::generalNameAsString captures the complete string including the NUL. However, when .c_str() evaluates it, implicit conversion to absl::string_view inside dnsNameMatch relies on strlen(), prematurely truncating the evaluation context. Envoy evaluates trucated string against the exact required config_san match and returns true, thereby successfully validating the string with the Nul byte for an upstream routing. This vulnerability is fixed in 1.35.11, 1.36.7, 1.37.3, and 1.38.1."}],"affected":[{"vendor":"envoyproxy","product":"envoy","versions":[{"version":">= 1.38.0, < 1.38.1","status":"affected"},{"version":">= 1.37.0, < 1.37.3","status":"affected"},{"version":">= 1.36.0, < 1.36.7","status":"affected"},{"version":"< 1.35.11","status":"affected"}]}],"references":[{"url":"https://github.com/envoyproxy/envoy/security/advisories/GHSA-f8x4-rw5x-f3r7","name":"https://github.com/envoyproxy/envoy/security/advisories/GHSA-f8x4-rw5x-f3r7","tags":["x_refsource_CONFIRM"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":4.4,"baseSeverity":"MEDIUM","confidentialityImpact":"HIGH","integrityImpact":"NONE","privilegesRequired":"HIGH","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-158","lang":"en","description":"CWE-158: Improper Neutralization of Null Byte or NUL Character","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-06-26T17:27:57.707Z"},"source":{"advisory":"GHSA-f8x4-rw5x-f3r7","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/envoyproxy/envoy/security/advisories/GHSA-f8x4-rw5x-f3r7","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-06-27T02:52:00.418621Z","id":"CVE-2026-47778","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-06-27T02:53:13.826Z"}}]}}}