The vulnerability in Erlang OTP's public_key:pkix_ocsp_validate/5 function arises because it does not cryptographically verify that a CA-designated OCSP responder certificate is signed by the issuing CA. Instead, it only checks the issuer name and the presence of the OCSPSigning extended key usage. An attacker able to intercept or control OCSP responses can create a self-signed certificate with a matching issuer name and OCSPSigning EKU to forge OCSP responses that incorrectly mark revoked certificates as valid. This affects SSL/TLS clients using OCSP stapling and any applications using the vulnerable API directly. The affected components include OTP versions 27.0 before 28.4.2 and 27.3.4.10, public_key versions from 1.16 before 1.20.3 and 1.17.1.2, and ssl versions 11.2 before 11.5.4 and 11.2.12.7. The vulnerability is tracked as CWE-295 (Improper Certificate Validation) and CWE-347 (Improper Verification of Cryptographic Signature).

The vulnerability allows attackers who can intercept or control OCSP responses to bypass OCSP designated-responder authorization, enabling them to forge OCSP responses that mark revoked certificates as valid. This can cause SSL/TLS clients using OCSP stapling to accept connections to servers with revoked certificates, potentially exposing sensitive data to compromised servers. Applications using the vulnerable API directly may also be impacted depending on their usage context.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. The Red Hat advisory linked does not explicitly state patch availability or mitigation steps. Users should monitor the official Erlang and Red Hat advisories for updates and apply any released patches promptly once available. Until then, consider disabling OCSP stapling or using alternative certificate revocation checking methods if feasible in your environment.