{"id":"CVE-2026-73251","aliases":["DEBIAN-CVE-2026-73251","EUVD-2026-63494","GHSA-qj6j-2692-v2r8","JLSEC-2026-1376","UBUNTU-CVE-2026-73251"],"status":"published","title":"Mongoose Built-in TLS: CA-bundle certificate chain accepted without any signature verification","description":"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.","severity":{"version":"4.0","score":9.3,"vector":"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","level":"critical","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00193,"percentile":0.09029,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-295"],"published":"2026-08-20T17:34:50Z","modified":"2026-10-28T11:23:01Z","fixes":[{"ecosystem":"Debian:14","package":"mongoose","fixed_in":["7.23+ds-1"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"Debian:14","package":"mongoose","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"7.23+ds-1"}]}],"versions":["7.21+ds-1","7.21+ds-1~bpo13+1","7.21+ds-2","7.22+ds-1","7.22+ds-1~bpo13+1","7.23+ds-1~bpo13+1"]},{"source":"osv","ecosystem":"Julia","package":"Mongoose_jll","ranges":[{"type":"SEMVER","events":[{"introduced":"0"}]}]},{"source":"osv","ecosystem":"Ubuntu:26.10","package":"mongoose","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["7.21+ds-1","7.21+ds-2","7.22+ds-1","7.23+ds-1"]}],"products":[{"vendor":"automattic","product":"mongoose"},{"vendor":"cesanta","product":"mongoose"}],"references":[{"url":"https://github.com/cesanta/mongoose/security/advisories/GHSA-qj6j-2692-v2r8","tags":["x_refsource_CONFIRM","x_refsource_MISC","Vendor Advisory","advisory","web"]},{"url":"https://github.com/cesanta/mongoose/commit/2988bc9df3a5efc9539471cb7455975fa25df483","tags":["x_refsource_MISC","Patch","fix","web"]},{"url":"https://github.com/cesanta/mongoose/releases/tag/7.23","tags":["x_refsource_MISC","Release Notes","web"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/73xxx/CVE-2026-73251.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-73251","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-73251","tags":["advisory"]},{"url":"https://ubuntu.com/security/CVE-2026-73251","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-73251","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-73251","title":"Mongoose Built-in TLS: CA-bundle certificate chain accepted without any signature verification","description":"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.","status":"published","published":"2026-08-20T17:34:50.472Z","modified":"2026-08-20T19:50:32.555Z","cvss":[{"version":"4.0","score":9.3,"vector":"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","level":"critical","assessor":"cna"}],"cwes":["CWE-295"],"updated_at":"2026-11-02T13:43:33.766176Z"}],"euvd":[{"id":"EUVD-2026-63494","description":"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.","status":"published","published":"2026-08-20T17:34:50Z","modified":"2026-08-20T19:50:32Z","cvss":[{"version":"4.0","score":9.3,"vector":"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","level":"critical"}],"updated_at":"2026-11-02T18:01:38.32409Z"}],"nvd":[{"id":"CVE-2026-73251","description":"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.","status":"published","published":"2026-08-20T18:16:45.743Z","modified":"2026-10-18T20:10:00.11Z","cvss":[{"version":"4.0","score":9.3,"vector":"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"critical","assessor":"secondary"},{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","level":"critical","assessor":"primary"}],"cwes":["CWE-295"],"updated_at":"2026-11-02T14:12:40.302911Z"}],"osv":[{"id":"CVE-2026-73251","title":"Mongoose Built-in TLS: CA-bundle certificate chain accepted without any signature verification","description":"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.","status":"published","published":"2026-08-20T17:34:50.472Z","modified":"2026-10-28T11:23:01.505518096Z","cvss":[{"version":"4.0","score":9.3,"vector":"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","level":"critical"}],"cwes":["CWE-295"],"updated_at":"2026-11-02T15:45:16.365946Z"},{"id":"DEBIAN-CVE-2026-73251","description":"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.","status":"published","published":"2026-08-20T18:16:45.743Z","modified":"2026-10-23T17:47:35.262815068Z","cvss":[{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","level":"critical"}],"updated_at":"2026-11-02T15:46:02.499355Z"},{"id":"JLSEC-2026-1376","description":"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-\u003e`ca_bundle_der` while tls-\u003e`ca_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.","status":"published","published":"2026-08-24T13:43:17.899Z","modified":"2026-08-24T14:00:03.406131973Z","cvss":[{"version":"4.0","score":9.3,"vector":"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"critical"}],"updated_at":"2026-11-02T15:47:18.159338Z"},{"id":"UBUNTU-CVE-2026-73251","description":"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.","status":"published","published":"2026-08-20T18:16:00Z","modified":"2026-10-17T13:01:01.830622416Z","cvss":[{"version":"4.0","score":9.3,"vector":"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","level":"critical"},{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","level":"critical"}],"updated_at":"2026-11-02T16:57:08.628462Z"}]}}