{"schemaVersion":3,"id":"CVE-2026-42791","aliases":["UBUNTU-CVE-2026-42791","DEBIAN-CVE-2026-42791"],"status":"published","duplicateOf":null,"title":null,"description":"Improper Certificate Validation vulnerability in Erlang OTP public_key (pubkey_ocsp module) allows forged OCSP responses signed with an expired responder certificate to be accepted as valid.\n\nOCSP response verification in pubkey_ocsp:verify_response/5 and pubkey_ocsp:is_authorized_responder/3 in lib/public_key/src/pubkey_ocsp.erl does not check the validity period (notBefore/notAfter) of the OCSP responder certificate. An attacker who has obtained the private key of an expired CA-designated OCSP responder certificate can forge OCSP responses that Erlang/OTP accepts as valid.\n\nThis affects TLS clients using OCSP stapling via the ssl application: a malicious or compromised server can present a revoked TLS certificate together with a forged OCSP response signed by an expired responder key, and the client will accept the revoked certificate as valid. It also affects applications calling public_key:pkix_ocsp_validate/5 directly, where the impact depends on the use case — server-side client certificate validation using this API may allow authentication bypass with a revoked client certificate.\n\nThis issue affects OTP from OTP 27.0 before OTP 29.0.1, OTP 28.5.0.1 and OTP 27.3.4.12, corresponding to public_key from 1.16 before 1.21.1, 1.20.3.1 and 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Certificate Validation","description":"The product does not validate, or incorrectly validates, a certificate.","type":"weakness","status":"Draft","abstraction":"Base","likelihoodOfExploit":null,"url":"https://cwe.mitre.org/data/definitions/295.html"},{"id":"CWE-672","name":"Operation on a Resource after Expiration or Release","description":"The product uses, accesses, or otherwise operates on a resource after that resource has been expired, released, or revoked.","type":"weakness","status":"Draft","abstraction":"Class","likelihoodOfExploit":null,"url":"https://cwe.mitre.org/data/definitions/672.html"}],"affected":[{"vendor":"debian","product":"erlang","name":"erlang","label":"erlang","ecosystem":"Debian","cpePart":null,"purl":"pkg:deb/debian/erlang","purlType":"deb","versions":[{"text":"< 1:27.3.4.1+dfsg-1+deb13u3","noFixRecorded":false,"fixedIn":null},{"text":"< 1:27.3.4.12+dfsg-1","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 1:27.3.4.1+dfsg-1+deb13u3 | < 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