CVE-2026-42791
LowCVSS 3.7Exploitation Probability (EPSS)
Low risk24th percentile - higher than 24% of all known CVEs
Summary
A vulnerability in Erlang OTP's public_key module (pubkey_ocsp) allows forged OCSP responses signed with an expired responder certificate to be accepted as valid. The validity period of the OCSP responder certificate is not checked.
Risk Assessment
The organization may accept revoked TLS certificates as valid, potentially compromising TLS connection security and allowing authentication bypass.
Recommendation
Upgrade Erlang OTP to version 29.0.1, 28.5.0.1, or 27.3.4.12 (or later). Also monitor OCSP responses and use additional verification mechanisms.
Original NVD description (English source)
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.