{"affected":[{"ranges":[{"events":[{"introduced":"2b1a742c651b90f8a7a1fb2ddde73f29915ea376"},{"fixed":"7995f1fdaee3da569bb810358ce0f546471d169b"},{"fixed":"b3870e02405c709a872b01ba6086065620cdfe76"}],"repo":"https://github.com/erlang/otp","type":"GIT"}]}],"aliases":["GHSA-cjxj-wj6x-3fff","CVE-2026-42791"],"credits":[{"name":"Jakub Witczak","type":"REMEDIATION_DEVELOPER"},{"name":"Ingela Anderton Andin","type":"REMEDIATION_REVIEWER"}],"database_specific":{"capec_ids":["CAPEC-475"],"cpe_ids":["cpe:2.3:a:erlang:erlang\\/otp:*:*:*:*:*:*:*:*"],"cwe_ids":["CWE-295","CWE-672"]},"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 27.3.4.12, 28.5.0.1, and 29.0.1 corresponding to public_key from 1.16 before 1.17.1.3, 1.20.3.1, and 1.21.1.\n\n## Workaround\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## Configuration\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.","id":"EEF-CVE-2026-42791","modified":"2026-05-27T15:41:07.758Z","published":"2026-05-27T12:23:13.584Z","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"}],"related":[],"schema_version":"1.7.3","severity":[{"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","type":"CVSS_V4"}],"summary":"OCSP responder certificate validity period not checked in public_key","upstream":[]}