CVE-2026-26007

Published: February 15, 2026Last modified: March 5, 2026

Description

cryptography is a package designed to expose cryptographic primitives and recipes to Python developers. Prior to 46.0.5, the public_key_from_numbers (or EllipticCurvePublicNumbers.public_key()), EllipticCurvePublicNumbers.public_key(), load_der_public_key() and load_pem_public_key() functions do not verify that the point belongs to the expected prime-order subgroup of the curve. This missing validation allows an attacker to provide a public key point P from a small-order subgroup. This can lead to security issues in various situations, such as the most commonly used signature verification (ECDSA) and shared key negotiation (ECDH). When the victim computes the shared secret as S = [victim_private_key]P via ECDH, this leaks information about victim_private_key mod (small_subgroup_order). For curves with cofactor > 1, this reveals the least significant bits of the private key. When these weak public keys are used in ECDSA , it's easy to forge signatures on the small subgroup. Only SECT curves are impacted by this. This vulnerability is fixed in 46.0.5.

Severity score breakdown

Notes

23 LTS is not affected because vulnerable code was introduced in version 42.0.0 in commit: https://github.com/pyca/cryptography/commit/f38eb4a0e45645e6a43f8dd589f1d3ce1103e83c

Status

References

• http://www.openwall.com/lists/oss-security/2026/02/10/4
• https://github.com/pyca/cryptography/commit/0eebb9dbb6343d9bc1d91e5a2482ed4e054a6d8c
• https://github.com/pyca/cryptography/security/advisories/GHSA-r6ph-v2qm-q3c2