CVE-2026-26007
Publication date 10 February 2026
Last updated 12 March 2026
Ubuntu priority
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.
Status
| Package | Ubuntu Release | Status |
|---|---|---|
| python-cryptography | 25.10 questing |
Fixed 43.0.0-1ubuntu1.1
|
| 24.04 LTS noble |
Fixed 41.0.7-4ubuntu0.3
|
|
| 22.04 LTS jammy |
Fixed 3.4.8-1ubuntu2.3
|
|
| 20.04 LTS focal |
Needs evaluation
|
|
| 18.04 LTS bionic |
Needs evaluation
|
|
| 16.04 LTS xenial |
Needs evaluation
|
Notes
mdeslaur
Per upstream release notes: "This issue only affects binary elliptic curves, which are rarely used in real-world applications." In noble and earlier releases, the EC backend did not use rust, see the following commit: https://github.com/pyca/cryptography/commit/f38eb4a0e45645e6a43f8dd589f1d3ce1103e83c
References
Related Ubuntu Security Notices (USN)
- USN-8087-1
- python-cryptography vulnerability
- 12 March 2026