{"schema_version":"1.9.0","id":"EEF-CVE-2026-42791","published":"2026-05-27T12:23:13.584Z","modified":"2026-09-08T03:30:05.422892489Z","aliases":["CVE-2026-42791","GHSA-cjxj-wj6x-3fff"],"summary":"OCSP responder certificate validity period not checked in public_key","details":"## Summary\n\nImproper 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 1.17.1.3.\n\n## Workarounds\n\n\\* For TLS clients using the ssl application, disable OCSP stapling by setting {stapling, no\\_staple} in the client options, or switch to CRL-based revocation checking with {crl\\_check, true}.\n\\* For applications calling public\\_key:pkix\\_ocsp\\_validate/5 directly, validate the responder certificate's validity period in application code before calling the function.\n\n## Configurations\n\nFor the ssl application, OCSP stapling must be enabled by setting the stapling option to staple in the TLS client options. OCSP stapling is not enabled by default.\n\nApplications calling public\\_key:pkix\\_ocsp\\_validate/5 directly are unconditionally affected when that function is used.","affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/erlang/otp","events":[{"introduced":"2b1a742c651b90f8a7a1fb2ddde73f29915ea376"},{"fixed":"7995f1fdaee3da569bb810358ce0f546471d169b"},{"fixed":"b3870e02405c709a872b01ba6086065620cdfe76"}]}],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-42791.json"}}],"references":[{"type":"ADVISORY","url":"https://github.com/erlang/otp/security/advisories/GHSA-cjxj-wj6x-3fff"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-42791.html"},{"type":"WEB","url":"https://www.erlang.org/doc/system/versions.html#order-of-versions"},{"type":"FIX","url":"https://github.com/erlang/otp/commit/7995f1fdaee3da569bb810358ce0f546471d169b"},{"type":"FIX","url":"https://github.com/erlang/otp/commit/b3870e02405c709a872b01ba6086065620cdfe76"}],"database_specific":{"capec_ids":["CAPEC-475"],"cpe_ids":["cpe:2.3:a:erlang:erlang\\/otp:*:*:*:*:*:*:*:*"],"cwe_ids":["CWE-295","CWE-672"]},"severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N"}],"credits":[{"name":"Jakub Witczak","type":"REMEDIATION_DEVELOPER"},{"name":"Ingela Anderton Andin","type":"REMEDIATION_REVIEWER"}]}