CVE-2020-12607
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^-1, 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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- None
- Availability
- None
Exploit likelihood
What each source reports
NVD Score used
7.5
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^-1, 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.
- Record
CVE-2020-12607- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - CVSS 2.0
- 5.0 Medium
AV:N/AC:L/Au:N/C:P/I:N/A:N - Weakness
- CWE-347
- Updated
- 2026-11-02
CVE List No score
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^-1, 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.
- Record
CVE-2020-12607- Updated
- 2026-11-02
EUVDEUVD-2020-0078 No score
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^-1, 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.
- Record
EUVD-2020-0078- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-56wv-2wr9-3h9r
8.7
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.
- Record
GHSA-56wv-2wr9-3h9r- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - Weakness
- CWE-347
- Updated
- 2026-11-02
OSV
7.5
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^-1, 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.
- Record
CVE-2020-12607- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - Updated
- 2026-11-02
OSVGHSA-56wv-2wr9-3h9r
8.7
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.
- Record
GHSA-56wv-2wr9-3h9r- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - Weakness
- CWE-347
- Updated
- 2026-11-02
OSVPYSEC-2020-42 No score
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^-1, 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.
- Record
PYSEC-2020-42- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
fastecdsaPyPI |
before 2.1.2 | 2.1.2 |
fastecdsaPyPI |
before 2.1.2, plus listed versions 1.0.0b11.0.11.0.1b11.0.1b21.0.1b3 Show 28 moreShow less1.0.21.0.31.1.01.1.11.1.21.1.31.2.11.3.11.3.21.4.11.4.21.4.31.5.11.5.21.6.11.6.21.6.31.6.41.6.51.7.01.7.11.7.21.7.31.7.41.7.52.0.02.1.02.1.1 |
2.1.2 |
fastecdsaPyPI |
before 2.1.2, plus listed versions 1.0.0b11.0.1b11.0.1b21.0.1b31.0.1 Show 28 moreShow less1.0.21.0.31.1.01.1.11.1.21.1.31.2.11.3.11.3.21.4.11.4.21.4.31.5.11.5.21.6.11.6.21.6.31.6.41.6.51.7.01.7.11.7.21.7.31.7.41.7.52.0.02.1.02.1.1 |
2.1.2 |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2020-12607 is a high vulnerability (CVSS 7.5) in Antonkueltz Fastecdsa, published June 2, 2020. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.31%, the 70th percentile. Fixed in fastecdsa 2.1.2.
References
github.com/AntonKueltz/fastecdsa/commit/4a16daeaf139be20654ef58a9fe4c79dc030458c
github.com/AntonKueltz/fastecdsa/issues/52
github.com/AntonKueltz/fastecdsa/commit/e592f106edd5acf6dacedfab2ad16fe6c735c9d1
github.com/AntonKueltz/fastecdsa/commit/7b64e3efaa806b4daaf73bb5172af3581812f8de
nvd.nist.gov/vuln/detail/CVE-2020-12607
github.com/advisories/GHSA-56wv-2wr9-3h9r
github.com/pypa/advisory-database/tree/main/vulns/fastecdsa/PYSEC-2020-42.yaml
github.com/AntonKueltz/fastecdsa