CVE-2026-26007

Name of the Vulnerable Software and Affected Versions cryptography versions prior to 46.0.5

Description A validation flaw exists where the functions public key from numbers() (or EllipticCurvePublicNumbers.public key()), EllipticCurvePublicNumbers.public key(), load der public key(), and load pem public key() fail to verify if a point belongs to the expected prime-order subgroup of the curve. This allows an attacker to provide a public key point P from a small-order subgroup, which specifically impacts SECT curves. This can lead to security issues during signature verification (ECDSA) and shared key negotiation (ECDH). In ECDH, when a victim computes the shared secret as S = [victim private key]P, information about victim private key mod (small subgroup order) is leaked. For curves with a cofactor greater than 1, this reveals the least significant bits of the private key. Additionally, using these weak public keys in ECDSA makes it possible to forge signatures on the small subgroup.

Recommendations Update cryptography to version 46.0.5.