{"id":"CVE-2021-43569","aliases":["GHSA-j3jw-j2j8-2wv9"],"url":"https://o3.security/vulnerability/CVE-2021-43569","summary":"Improper Verification of Cryptographic Signature in starkbank-ecdsa","details":"The verify function in the Stark Bank .NET ECDSA library (ecdsa-dotnet) 1.3.1 fails to check that the signature is non-zero, which allows attackers to forge signatures on arbitrary messages.","published":"2021-11-09T22:15:07.597Z","modified":"2026-07-09T05:45:33.583544Z","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":{"score":0.01022,"percentile":0.60344,"asOf":"2026-08-23"},"cisaKev":null,"exploitsKnown":1,"affectedPackages":[{"ecosystem":"NuGet","name":"starkbank-ecdsa","fixedVersion":"1.3.2"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/starkbank/ecdsa-dotnet/releases/tag/v1.3.2"},{"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":"2026-07-09T05:45:33.583544Z"}}