CVE-2026-25793: Blocklist Bypass possible via ECDSA Signature Malleability

(updated )

When using P256 certificates (which is not the default configuration), it is possible to evade a blocklist entry created against the fingerprint of a certificate by using ECDSA Signature Malleability to use a copy of the certificate with a different fingerprint.

In order for this to affect a user or network, all of the following must be true:

  • CURVE_P256 certificates are being used
  • There are one or more entries on the blocklist
  • The certificates for those entries are signed by a trusted CA and not expired
  • An attacker has a copy of the private key, and corresponding certificate, for one of those blocklist entries

References

Code Behaviors & Features

Detect and mitigate CVE-2026-25793 with GitLab Dependency Scanning

Secure your software supply chain by verifying that all open source dependencies used in your projects contain no disclosed vulnerabilities. Dependency Scanning using SBOM also detects vulnerabilities from proprietary advisories that this site does not include. Learn more about Dependency Scanning using SBOM →