What’s Vulnerable › Vulnerabilities

CVE-2020-12607

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.3% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2020-06-02 · updated 2026-06-17
• Weakness: CWE-347

Description

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

• fastecdsa: before 2.1.2 — fixed in 2.1.2

How to fix

Upgrade to a fixed version: fastecdsa 2.1.2. Check the vendor advisory for mitigations.

References

• https://github.com/AntonKueltz/fastecdsa/commit/4a16daeaf139be20654ef58a9fe4c79dc030458c
• https://github.com/AntonKueltz/fastecdsa/commit/7b64e3efaa806b4daaf73bb5172af3581812f8de
• https://github.com/AntonKueltz/fastecdsa/commit/e592f106edd5acf6dacedfab2ad16fe6c735c9d1
• https://github.com/AntonKueltz/fastecdsa/issues/52
• https://github.com/AntonKueltz/fastecdsa/commit/4a16daeaf139be20654ef58a9fe4c79dc030458c
• https://github.com/AntonKueltz/fastecdsa/commit/7b64e3efaa806b4daaf73bb5172af3581812f8de
• https://github.com/AntonKueltz/fastecdsa/commit/e592f106edd5acf6dacedfab2ad16fe6c735c9d1
• https://github.com/AntonKueltz/fastecdsa/issues/52

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