CVE-2026-33936
The `ecdsa` PyPI package is a pure Python implementation of ECC (Elliptic Curve Cryptography) with support for ECDSA (Elliptic Curve Digital Signature Algorith…
Impact
The `ecdsa` PyPI package is a pure Python implementation of ECC (Elliptic Curve Cryptography) with support for ECDSA (Elliptic Curve Digital Signature Algorithm), EdDSA (Edwards-curve Digital Signature Algorithm) and ECDH (Elliptic Curve Diffie-Hellman). Prior to version 0.19.2, an issue in the low-level DER parsing functions can cause unexpected exceptions to be raised from the public API functions. `ecdsa.der.remove_octet_string()` accepts truncated DER where the encoded length exceeds the available buffer. For example, an OCTET STRING that declares a length of 4096 bytes but provides only 3 bytes is parsed successfully instead of being rejected. Because of that, a crafted DER input can cause `SigningKey.from_der()` to raise an internal exception (`IndexError: index out of bounds on dimension 1`) rather than cleanly rejecting malformed DER (e.g., raising `UnexpectedDER` or `ValueError`). Applications that parse untrusted DER private keys may crash if they do not handle unexpected exceptions, resulting in a denial of service. Version 0.19.2 patches the issue.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| pip | ecdsa | < 0.19.2 | 0.19.2 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Tlsfuzzer | Ecdsa | before 0.19.2 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/tlsfuzzer/python-ecdsa/commit/bd66899550d7185939bf27b75713a2ac9325a9d3
- https://github.com/tlsfuzzer/python-ecdsa/releases/tag/python-ecdsa-0.19.2
- https://github.com/tlsfuzzer/python-ecdsa/security/advisories/GHSA-9f5j-8jwj-x28g
- https://github.com/advisories/GHSA-9f5j-8jwj-x28g
- https://nvd.nist.gov/vuln/detail/CVE-2026-33936