{"id":"DEBIAN-CVE-2026-42791","details":"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.  OCSP 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.  This 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.  This 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 1.17.1.3.","modified":"2026-08-27T23:05:49.516535084Z","published":"2026-05-27T14:16:53.460Z","upstream":["CVE-2026-42791"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-42791"}],"affected":[{"package":{"name":"erlang","ecosystem":"Debian:13","purl":"pkg:deb/debian/erlang?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1:27.3.4.1+dfsg-1+deb13u3"}]}],"versions":["1:27.3.4.1+dfsg-1","1:27.3.4.1+dfsg-1+deb13u1","1:27.3.4.1+dfsg-1+deb13u2"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-42791.json"}},{"package":{"name":"erlang","ecosystem":"Debian:14","purl":"pkg:deb/debian/erlang?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1:27.3.4.12+dfsg-1"}]}],"versions":["1:27.3.4.1+dfsg-1","1:27.3.4.10+dfsg-1","1:27.3.4.11+dfsg-1","1:27.3.4.11+dfsg-2","1:27.3.4.11+dfsg-3","1:27.3.4.11+dfsg-4","1:27.3.4.11+dfsg-5","1:27.3.4.11+dfsg-6","1:27.3.4.11+dfsg-7","1:27.3.4.3+dfsg-1","1:27.3.4.4+dfsg-1","1:27.3.4.6+dfsg-1","1:27.3.4.8+dfsg-1","1:27.3.4.9+dfsg-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-42791.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N"}]}