{"id":"CVE-2026-73251","summary":"Mongoose Built-in TLS: CA-bundle certificate chain accepted without any signature verification","details":"Mongoose is an embedded web server and network library. Prior to 7.23, a network attacker can impersonate a TLS server to a Mongoose client configured with a multi-certificate CA bundle. In src/tls_builtin.c, the mg_tls_init() function stores the bundle in tls-\u003eca_bundle_der while tls-\u003eca_der.len remains zero, and mg_tls_recv_cert() uses tls_bundle_find() to accept a Common Name match without calling mg_tls_verify_cert_signature(). A forged self-signed certificate can therefore satisfy hostname and CertificateVerify checks and enable interception, credential disclosure, traffic modification, and malicious responses. This issue is fixed in version 7.23.","aliases":["GHSA-qj6j-2692-v2r8"],"modified":"2026-09-11T08:36:51.669958Z","published":"2026-08-20T17:34:50.472Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/73xxx/CVE-2026-73251.json","cna_assigner":"GitHub_M","cwe_ids":["CWE-295"]},"references":[{"type":"WEB","url":"https://github.com/cesanta/mongoose/releases/tag/7.23"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/73xxx/CVE-2026-73251.json"},{"type":"ADVISORY","url":"https://github.com/cesanta/mongoose/security/advisories/GHSA-qj6j-2692-v2r8"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-73251"},{"type":"FIX","url":"https://github.com/cesanta/mongoose/commit/2988bc9df3a5efc9539471cb7455975fa25df483"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/cesanta/mongoose","events":[{"introduced":"0"},{"fixed":"2988bc9df3a5efc9539471cb7455975fa25df483"},{"fixed":"02bdbb9ed6f0a8f7c42228c6e7cb35d748b60551"}],"database_specific":{"source":["AFFECTED_FIELD","REFERENCES"],"extracted_events":[{"introduced":"0"},{"fixed":"7.23"}]}}],"versions":["7.22","7.21","7.20","7.19","7.18","7.17","7.16","7.15","7.14","7.13","7.12","7.11","7.8","7.7","7.6","7.5","7.4","7.3","7.2","7.1","7.0","6.18","6.17","6.16","6.15","6.14","6.13","6.12","6.11","6.10","6.9","6.7","6.6","6.5","6.4","6.3","6.2","6.1","6.0","5.6","5.5_20140120","5.5","5.4","5.3","5.2","5.1","5.0","4.1","4.0","3.8","3.7","3.6","3.5","3.4","3.3","3.2"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-73251.json","vanir_signatures_modified":"2026-09-11T08:36:51Z","vanir_signatures":[{"signature_version":"v1","source":"https://github.com/cesanta/mongoose/commit/2988bc9df3a5efc9539471cb7455975fa25df483","target":{"file":"mongoose.c"},"deprecated":false,"digest":{"line_hashes":["280880759204458332186591428807639899707","91784847098628061190181036714616550317","260324905700960565902262748823032487472","1462060790025201554329754208352907614"],"threshold":0.9},"id":"CVE-2026-73251-4e9d2e62","signature_type":"Line"},{"target":{"file":"src/tls_builtin.c","function":"mg_tls_recv_cert"},"deprecated":false,"digest":{"function_hash":"179946136510036810370347435467022032985","length":4038},"id":"CVE-2026-73251-7aa16f5b","signature_type":"Function","signature_version":"v1","source":"https://github.com/cesanta/mongoose/commit/2988bc9df3a5efc9539471cb7455975fa25df483"},{"signature_version":"v1","source":"https://github.com/cesanta/mongoose/commit/2988bc9df3a5efc9539471cb7455975fa25df483","target":{"file":"mongoose.c","function":"mg_tls_recv_cert"},"deprecated":false,"digest":{"length":4038,"function_hash":"179946136510036810370347435467022032985"},"id":"CVE-2026-73251-b716628b","signature_type":"Function"},{"id":"CVE-2026-73251-d2542a77","signature_type":"Line","signature_version":"v1","source":"https://github.com/cesanta/mongoose/commit/2988bc9df3a5efc9539471cb7455975fa25df483","target":{"file":"src/tls_builtin.c"},"deprecated":false,"digest":{"line_hashes":["280880759204458332186591428807639899707","91784847098628061190181036714616550317","260324905700960565902262748823032487472","1462060790025201554329754208352907614"],"threshold":0.9}}]}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N"}]}