CVE-2021-43572

Name: CVE-2021-43572
Creator: NVD / NIST
Published: 2021-11-09T22:15:07.727+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 1.20%

Last modified Jun 17, 2026

CVE-2021-43572 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. 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.. EPSS estimates a 1.20% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

1.20%

64.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-347

Affected Software

Vendor	Product	Versions
Starkbank	Ecdsa-Python	< 2.0.1

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

Timeline

Published: Nov 9, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-43572?

How severe is CVE-2021-43572?

CVE-2021-43572 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 1.20% probability of exploitation in the next 30 days.

How do I fix CVE-2021-43572?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-43572?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST