How severe is CVE-2021-43572?

CVE-2021-43572 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-43572 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (64th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-43572?

CVE-2021-43572 affects Starkbank Ecdsa-python. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-43572?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-43572 published?

CVE-2021-43572 was published on 2021-11-09 and last updated on 2026-06-17.

CVE-2021-43572

CVE-2021-43572 is a critical-severity vulnerability in Starkbank Ecdsa-python with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-347.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 1% (64th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-347
Affected product: Starkbank Ecdsa-python
Published: 2021-11-09
Last modified: 2026-06-17

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.

Frequently asked questions

What is 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.
How severe is CVE-2021-43572?: CVE-2021-43572 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-43572 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (64th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-43572?: CVE-2021-43572 affects Starkbank Ecdsa-python. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-43572?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-43572 published?: CVE-2021-43572 was published on 2021-11-09 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:starkbank:ecdsa-python:*:*:*:*:*:*:*:*

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