CVE-2021-43572
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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (1.25%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
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.
- CVSS 3.1
- 9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 1.25% probability · 69th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-347
- Affected
- starkbank/ecdsa-python
- Source
- cve@mitre.org
EPSS 1.2% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://github.com/starkbank/ecdsa-python/commit/d136170666e9510eb63c2572551805807bd4c17fPatch, Third Party Advisory
- https://github.com/starkbank/ecdsa-python/releases/tag/v2.0.1Release Notes, Third Party Advisory
- https://research.nccgroup.com/2021/11/08/technical-advisory-arbitrary-signature-forgery-in-stark-bank-ecdsa-libraries/Exploit, Third Party Advisory
- https://github.com/starkbank/ecdsa-python/commit/d136170666e9510eb63c2572551805807bd4c17fPatch, Third Party Advisory
- https://github.com/starkbank/ecdsa-python/releases/tag/v2.0.1Release Notes, Third Party Advisory
- https://research.nccgroup.com/2021/11/08/technical-advisory-arbitrary-signature-forgery-in-stark-bank-ecdsa-libraries/Exploit, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.