CVE-2020-12607: Antonkueltz Fastecdsa

High severity, CVSS 7.5. EPSS: 1.3% chance of exploitation in the next 30 days.

An issue was discovered in fastecdsa before 2.1.2. When using the NIST P-256 curve in the ECDSA implementation, the point at infinity is mishandled. This means that for an extreme value in k and s^-1, the signature verification fails even if the signature is correct. This behavior is not solely a usability problem. There are some threat models where an attacker can benefit by successfully guessing users for whom signature verification will fail.

Affected products

• Antonkueltz Fastecdsa: before 2.1.2 (fixed in 2.1.2)

Published 2020-06-02. Last modified 2026-06-17.