{"id":"CVE-2026-66402","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-66402","generatedAt":"2026-10-28T03:41:00.664Z","title":"FreeRDP before 3.29.0 (affected versions <= 3.28.0) contains multiple TLS certificate identity validation weaknesses in tls_verify_certificate(), tls_match_hostname(), and x509_utils_get_dns_names().","description":"FreeRDP before 3.29.0 (affected versions <= 3.28.0) contains multiple TLS certificate identity validation weaknesses in tls_verify_certificate(), tls_match_hostname(), and x509_utils_get_dns_names(). Because FreeRDP performs custom Common Name and DNS SAN string matching instead of using OpenSSL's length-aware identity validation APIs, it (1) truncates DNS SAN values at embedded NUL bytes (accepting e.g. 'victim.example\\0.attacker.example' as 'victim.example'), (2) accepts a matching Common Name even when non-matching DNS SAN entries are present, and (3) accepts IP-literal targets via DNS/CN matching without comparing iPAddress SANs. Under a trusted or misissued certificate chain, an attacker positioned to present such a certificate can bypass server identity verification, weakening TLS server authentication.","published":"2026-08-01T13:16:57.000Z","lastModified":"2026-10-02T19:08:14.000Z","status":"Analyzed","sourceIdentifier":"disclosure@vulncheck.com","cvss":{"version":"4.0","score":9.3,"severity":"CRITICAL","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/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/M"},"cwe":["CWE-295"],"affected":["freerdp/freerdp"],"epss":{"score":0.0034,"percentile":0.27227,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.34%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://github.com/FreeRDP/FreeRDP/commit/b9533f07f98c25ed01c5f543b4d0ce73e120f5fd","tags":["Patch"],"source":"disclosure@vulncheck.com"},{"url":"https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-43hh-p3vw-hfx3","tags":["Vendor Advisory","Exploit","Mitigation"],"source":"disclosure@vulncheck.com"},{"url":"https://www.vulncheck.com/advisories/freerdp-before-tls-certificate-identity-validation-bypass","tags":["Patch","Third Party Advisory"],"source":"disclosure@vulncheck.com"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-66402","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}