This vulnerability stems from Botan’s omission of signature verification on OCSP responses during X509 path validation. As a result, a malicious actor can supply a forged OCSP response that the library accepts, allowing a man‑in‑the‑middle attack to bypass certificate revocation checks. The consequence is that a client may trust a revoked or compromised certificate, potentially enabling disclosure, tampering, or impersonation over TLS connections.

The flaw is present in randombit’s Botan library, affecting all releases from version 3.0.0 through the last release before 3.11.0. Versions 3.11.0 and later include a patch that reinstates proper signature verification.

The CVSS score of 5.9 indicates moderate severity. Exploitation requires that the attacker can supply a rogue OCSP response, usually by being in a position to influence the client’s certificate validation, such as a compromised or malicious relay. There is no EPSS metric available, and the vulnerability is not listed in the CISA KEV catalog, suggesting it has not been widely leveraged yet. Nevertheless, any environment where certificate revocation is critical should treat this as a real risk.