Botan’s ocsp_check utility in versions 1.11.34 through 3.13.0 does not verify the authenticity of OCSP responses it receives. A responder that returns a timely GOOD response with an empty, invalid, or unsigned signature can make a revoked certificate appear valid. The weakness, documented as CWE‑347, allows an attacker to bypass revocation checks by tricking the tool into accepting an unauthenticated response, potentially leading to the use of a compromised or revoked credential.

The vulnerability affects the RandomBit Botan cryptographic library, specifically the command‑line ocsp_check tool. Versions from 1.11.34 up to, but not including, 3.13.0 are impacted. Only the CLI is affected; library code used by applications is not vulnerable.

The CVSS score of 5.9 indicates moderate severity. No EPSS score is available, and the issue is not listed in the CISA KEV catalog. Exploitation requires control of an OCSP responder or an attacker on the network path to supply a forged response. Because the flaw is in a standalone command‑line tool, the practical attack surface is limited to environments that rely on ocsp_check for certificate verification. However, failure to detect a revoked certificate can lead to misuse of the certificate in downstream applications.