The Vulnerability OCSP designated‑responder authorization bypass originates from the public_key:pkix_ocsp_validate/5 function in Erlang OTP, which fails to verify that a CA‑designated responder certificate is cryptographically signed by its issuing CA. Instead, it only checks for a matching issuer name and the presence of the OCSPSigning extended key usage. This flaw, classified as CWE‑295 and CWE‑347, enables an attacker who can influence or intercept OCSP responses to construct a self‑signed responder certificate with a matching issuer name and the required EKU, thereby forging OCSP responses that falsely mark revoked certificates as valid. The consequence is that SSL/TLS clients accepting such stapled responses may establish connections to servers whose certificates have been revoked, potentially exposing sensitive data to malicious servers.

The flaw affects Erlang: OTP versions from 27.0 through 28.4.2 and 27.3.4.10, which correspond to public_key releases 1.16 through 1.20.3 and 1.17.1.2, as well as ssl releases 11.2 through 11.5.4 and 11.2.12.7. No other vendors or products are listed in the CNA data.

With a CVSS base score of 7.6 the vulnerability is considered high risk. The EPSS score is not available, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. Based on the description, exploitation likely requires the attacker to control or observe OCSP traffic, such as by operating a malicious OCSP responder or performing a man‑in‑the‑middle attack. If successful, the attacker can forge responses and cause TLS clients to accept revoked certificates, potentially exposing confidentiality and integrity of the transported data.