{"id":"CVE-2021-43569","aliases":["EUVD-2021-2359","GHSA-j3jw-j2j8-2wv9"],"status":"published","title":"Improper Verification of Cryptographic Signature in starkbank-ecdsa","description":"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.","severity":{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical","assessor":"primary","from":"nvd"},"epss":{"day":"2026-11-09","score":0.01056,"percentile":0.64665,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-347"],"published":"2021-11-09T21:05:06Z","modified":"2026-10-20T10:54:08Z","fixes":[{"ecosystem":"NuGet","package":"starkbank-ecdsa","fixed_in":["1.3.2"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"NuGet","package":"starkbank-ecdsa","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.3.2"}]}]},{"source":"osv","ecosystem":"NuGet","package":"starkbank-ecdsa","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.3.2"}]}],"versions":["0.0.1","1.0.0","1.1.0","1.2.0","1.2.1","1.3.0","1.3.1"]}],"products":[{"vendor":"starkbank","product":"ecdsa-dotnet"}],"references":[{"url":"https://research.nccgroup.com/2021/11/08/technical-advisory-arbitrary-signature-forgery-in-stark-bank-ecdsa-libraries/","tags":["x_refsource_MISC","x_transferred","Exploit","Third Party Advisory","evidence"]},{"url":"https://github.com/starkbank/ecdsa-dotnet/releases/tag/v1.3.2","tags":["x_refsource_MISC","x_transferred","Third Party Advisory","advisory","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-43569","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-j3jw-j2j8-2wv9"},{"url":"https://github.com/starkbank/ecdsa-dotnet","tags":["package"]},{"url":"https://research.nccgroup.com/2021/11/08/technical-advisory-arbitrary-signature-forgery-in-stark-bank-ecdsa-libraries","tags":["web"]}],"sources":{"cve":[{"id":"CVE-2021-43569","description":"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.","status":"published","published":"2021-11-09T21:05:06Z","modified":"2024-08-04T04:03:07.93Z","updated_at":"2026-11-02T14:32:56.689433Z"}],"euvd":[{"id":"EUVD-2021-2359","description":"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.","status":"published","published":"2021-11-09T21:05:06Z","modified":"2024-08-04T04:03:07Z","updated_at":"2026-11-03T03:24:13.772922Z"}],"ghsa":[{"id":"GHSA-j3jw-j2j8-2wv9","title":"Improper Verification of Cryptographic Signature in starkbank-ecdsa","description":"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.","status":"published","published":"2021-11-10T20:58:03Z","modified":"2023-02-01T05:06:31Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical"}],"cwes":["CWE-347"],"updated_at":"2026-11-02T14:36:39.086869Z"}],"nvd":[{"id":"CVE-2021-43569","description":"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.","status":"published","published":"2021-11-09T22:15:07.597Z","modified":"2026-06-17T04:11:09.137Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical","assessor":"primary"},{"version":"2.0","score":7.5,"vector":"AV:N/AC:L/Au:N/C:P/I:P/A:P","level":"high","assessor":"primary"}],"cwes":["CWE-347"],"updated_at":"2026-11-02T14:07:00.984108Z"}],"osv":[{"id":"CVE-2021-43569","description":"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.","status":"published","published":"2021-11-09T22:15:07.597Z","modified":"2026-10-20T10:54:08.679628581Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical"}],"updated_at":"2026-11-02T15:44:21.877444Z"},{"id":"GHSA-j3jw-j2j8-2wv9","title":"Improper Verification of Cryptographic Signature in starkbank-ecdsa","description":"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.","status":"published","published":"2021-11-10T20:58:03Z","modified":"2024-02-17T05:34:44.265885Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical"}],"cwes":["CWE-347"],"updated_at":"2026-11-02T15:46:49.977351Z"}]}}