Improper Verification of Cryptographic Signature in fastecdsa
An issue was discovered in fastecdsa before 2.1.2. When using the NIST P-256 curve in the ECDSA implementation, the point at infinity is mishandled. This means that for an extreme value in k and s<sup>-1</sup>, the signature verification fails even if the signature is correct. This behavior is not solely a usability problem. There are some threat models where an attacker can benefit by successfully guessing users for whom signature verification will fail.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | fastecdsa | < 2.1.2 | 2.1.2 |
References
- https://github.com/AntonKueltz/fastecdsa/commit/4a16daeaf139be20654ef58a9fe4c79dc030458c
- https://github.com/AntonKueltz/fastecdsa/commit/7b64e3efaa806b4daaf73bb5172af3581812f8de
- https://github.com/AntonKueltz/fastecdsa/issues/52
- https://github.com/AntonKueltz/fastecdsa/commit/e592f106edd5acf6dacedfab2ad16fe6c735c9d1
- https://github.com/advisories/GHSA-56wv-2wr9-3h9r
- https://nvd.nist.gov/vuln/detail/CVE-2020-12607
- https://github.com/AntonKueltz/fastecdsa
- https://github.com/pypa/advisory-database/tree/main/vulns/fastecdsa/PYSEC-2020-42.yaml
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N- Weakness (CWE)
CWE-347- Platform
- Python (PyPI)
- Package
fastecdsa- Disclosed
- 02.06.2020
- Updated
- 11.10.2026 12:19
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2020-42 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-56wv-2wr9-3h9r - CC BY 4.0
Vulnerability history: fastecdsa
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 2
- First → latest
- 06.2020 02.2024
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 2
Disclosures per year
- 2020: 1
- 2021: 0
- 2022: 0
- 2023: 0
- 2024: 1
- 2025: 0
- 2026: 0
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Improper Verification of Cryptographic Signature in fastecdsa this entry
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