{"id":"CVE-2020-12607","aliases":["GHSA-56wv-2wr9-3h9r","PYSEC-2020-42"],"url":"https://o3.security/vulnerability/CVE-2020-12607","summary":"Improper Verification of Cryptographic Signature in fastecdsa","details":"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.","published":"2020-06-02T21:15:10.607Z","modified":"2026-07-08T19:03:00.669603Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":1,"affectedPackages":[{"ecosystem":"PyPI","name":"fastecdsa","fixedVersion":"2.1.2"}],"fix":{"url":"https://github.com/AntonKueltz/fastecdsa/commit/4a16daeaf139be20654ef58a9fe4c79dc030458c","label":"AntonKueltz/fastecdsa@4a16dae"},"references":[{"type":"FIX","url":"https://github.com/AntonKueltz/fastecdsa/commit/4a16daeaf139be20654ef58a9fe4c79dc030458c"},{"type":"FIX","url":"https://github.com/AntonKueltz/fastecdsa/commit/7b64e3efaa806b4daaf73bb5172af3581812f8de"},{"type":"FIX","url":"https://github.com/AntonKueltz/fastecdsa/commit/e592f106edd5acf6dacedfab2ad16fe6c735c9d1"},{"type":"EVIDENCE","url":"https://github.com/AntonKueltz/fastecdsa/issues/52"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-08T19:03:00.669603Z"}}