{"id":"CVE-2021-43572","aliases":["GHSA-92vm-mxjf-jqf3","PYSEC-2021-426"],"url":"https://o3.security/vulnerability/CVE-2021-43572","summary":"Improper Verification of Cryptographic Signature in starkbank-ecdsa","details":"The verify function in the Stark Bank Python ECDSA library (aka starkbank-escada or ecdsa-python) before 2.0.1 fails to check that the signature is non-zero, which allows attackers to forge signatures on arbitrary messages.","published":"2021-11-09T22:15:07.727Z","modified":"2026-07-09T00:22:31.969615Z","cvss":{"score":9.8,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":1,"affectedPackages":[{"ecosystem":"PyPI","name":"starkbank-ecdsa","fixedVersion":"2.0.1"}],"fix":{"url":"https://github.com/starkbank/ecdsa-python/commit/d136170666e9510eb63c2572551805807bd4c17f","label":"starkbank/ecdsa-python@d136170"},"references":[{"type":"ADVISORY","url":"https://github.com/starkbank/ecdsa-python/releases/tag/v2.0.1"},{"type":"FIX","url":"https://github.com/starkbank/ecdsa-python/commit/d136170666e9510eb63c2572551805807bd4c17f"},{"type":"EVIDENCE","url":"https://research.nccgroup.com/2021/11/08/technical-advisory-arbitrary-signature-forgery-in-stark-bank-ecdsa-libraries/"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-09T00:22:31.969615Z"}}