CVE-2026-26007
MediumCVSS 6.5Exploitation Probability (EPSS)
Low risk26th percentile - higher than 26% of all known CVEs
Summary
In the cryptography library before version 46.0.5, there is a missing validation that the public key point belongs to the expected prime-order subgroup of the curve. This affects functions like public_key_from_numbers, load_der_public_key, and load_pem_public_key, allowing an attacker to provide a point from a small-order subgroup. Only SECT curves are impacted, potentially leading to private key leakage in ECDH and signature forgery in ECDSA.
Risk Assessment
The organization risks leakage of the least significant bits of the private key during ECDH key exchange and the possibility of ECDSA signature forgery, which could compromise data confidentiality and integrity.
Recommendation
Immediately update the cryptography library to version 46.0.5 or later, which includes the fix for public key point validation.
Original NVD description (English source)
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.