CVE-2021-43569 json
Improper Verification of Cryptographic Signature in starkbank-ecdsa
published 2021-11-09 4 y ago modified 2026-06-17 4 mo ago also GHSA-j3jw-j2j8-2wv9 , EUVD-2021-2359
- cvss
- 9.8
- version 3.1, NVD
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 1.1%
- EPSS 1.1% chance of exploitation in 30 days, percentile 64%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
Exploit prediction
1.06% chance of exploitation in the next 30 days, higher than 64% of all scored CVEs (FIRST EPSS, 2026-11-08).
Exploits and checks
- research.nccgroup.com https://research.nccgroup.com/2021/11/08/technical-advisory-arbitrary-signature-forgery-in-stark-bank-ecdsa-libraries/ referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| NVD | 3.1 | 9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| NVD | 2.0 | 7.5 | AV:N/AC:L/Au:N/C:P/I:P/A:P |
| GitHub | 3.1 | 9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| nuget | starkbank-ecdsa | <1.3.2 |
1.3.2 |
Classification
- Weakness
-
- CWE-347 Improper Verification of Cryptographic Signature
References
-
research.nccgroup.com
/2021/11/08/technical-advisory-arbitrary-signature-forgery-in-stark-bank-ecdsa-libraries/
exploit, third-party-advisory
-
github.com
/starkbank/ecdsa-dotnet/releases/tag/v1.3.2
web, third-party-advisory
-
nvd.nist.gov
/vuln/detail/CVE-2021-43569
advisory
-
github.com
/starkbank/ecdsa-dotnet
package
-
research.nccgroup.com
/2021/11/08/technical-advisory-arbitrary-signature-forgery-in-stark-bank-ecdsa-libraries
web
Sources
- CVE List CVE-2021-43569
- GitHub Advisory GHSA-j3jw-j2j8-2wv9
- NVD CVE-2021-43569
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