The vulnerability in the Botan cryptography library arises from missing verification of the OCSP response signature during X509 path validation in versions 3.0.0 through 3.10.x. Because the library does not check that the OCSP response is properly signed, an attacker can supply a forged response that indicates a certificate is valid even when it has been revoked. This flaw allows a man‑in‑the‑middle attacker to bypass certificate revocation checks, potentially compromising the confidentiality and integrity of secure communications.

This issue affects the Cryptography Library Botan developed by randombit. Versions starting from 3.0.0 up to, but not including, 3.11.0 are vulnerable. The patch that fixes the problem was released in Botan 3.11.0.

The CVSS score is 5.9, indicating moderate severity. The EPSS score is below 1%, suggesting a low likelihood of exploitation. The flaw is not listed in the CISA Known Exploited Vulnerabilities catalog. An attacker would need to deliver a crafted OCSP response to a software component that trusts the botan library. Usually this would occur over a network path where the application performs certificate validation, so the attack vector is inferred to be remote network‑based. Exploitation requires that the application accept the forged response as valid, which it will if the library is in the affected version range.