What’s Vulnerable › Vulnerabilities

CVE-2021-43572

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.2% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-11-09 · updated 2026-06-17
• Weakness: CWE-347

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.

Affected products

• Starkbank Ecdsa-Python: before 2.0.1 — fixed in 2.0.1

How to fix

Upgrade to a fixed version: Starkbank Ecdsa-Python 2.0.1. Check the vendor advisory for mitigations.

References

• https://github.com/starkbank/ecdsa-python/commit/d136170666e9510eb63c2572551805807bd4c17f
• https://github.com/starkbank/ecdsa-python/releases/tag/v2.0.1
• https://research.nccgroup.com/2021/11/08/technical-advisory-arbitrary-signature-forgery-in-stark-bank-ecdsa-libraries/
• https://github.com/starkbank/ecdsa-python/commit/d136170666e9510eb63c2572551805807bd4c17f
• https://github.com/starkbank/ecdsa-python/releases/tag/v2.0.1
• https://research.nccgroup.com/2021/11/08/technical-advisory-arbitrary-signature-forgery-in-stark-bank-ecdsa-libraries/

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