A vulnerability (CVE-2026-26007, CVSS 6.5) in the python-cryptography library involves incorrect subgroup validation for SECT curves, allowing a remote attacker to perform a subgroup attack and potentially recover the least significant bits of private keys. The vulnerability affects cryptography.io versions prior to 46.0.5. The fix is to upgrade to version 46.0.5.
Ubuntu Security Notices USN-8087-3 USN-8087-3: python-cryptography vulnerability Publication date 28 April 2026 Overview python-cryptography could be made to expose sensitive information over the network. Releases 20.04 LTS 18.04 LTS 16.04 LTS Open side navigation Close side navigation Packages Details Update instructions References Related notices Packages python-cryptography - Cryptography Python library Details USN-8087-1 fixed a vulnerability in python-cryptography. This update provides the corresponding update to Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, and Ubuntu 20.04 LTS. Original advisory details: It was discovered that python-cryptography incorrectly handled subgroup validation for SECT curves. A remote attacker could use this issue to perform a subgroup attack and possibly recover the least significant bits of private keys. USN-8087-1 fixed a vulnerability in python-cryptography. This update provides the corresponding update to Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, and Ubuntu 20.04 LTS. Original advisory details: It was discovered that python-cryptography incorrectly handled subgroup validation for SECT curves. A remote attacker could use this issue to perform a subgroup attack and possibly recover the least significant bits of private keys. Update instructions In general, a standard system update will make all the necessary changes. Learn more about how to get the fixes. The problem can be corrected by updating your system to the following package versions: Ubuntu Release Package Version 20.04 LTS focal python-cryptography – 2.8-3ubuntu0.3+esm2 Ubuntu Pro Fix available with Ubuntu Pro . python3-cryptography – 2.8-3ubuntu0.3+esm2 Ubuntu Pro Fix available with Ubuntu Pro . 18.04 LTS bionic python-cryptography – 2.1.4-1ubuntu1.4+esm3 Ubuntu Pro Fix available with Ubuntu Pro . python3-cryptography – 2.1.4-1ubuntu1.4+esm3 Ubuntu Pro Fix available with Ubuntu Pro . 16.04 LTS xenial python-cryptography – 1.2.3-1ubuntu0.3+esm3 Ubuntu Pro Fix available with Ubuntu Pro . python3-cryptography – 1.2.3-1ubuntu0.3+esm3 Ubuntu Pro Fix available with Ubuntu Pro . Reduce your security exposure Ubuntu Pro provides ten-year security coverage to 25,000+ packages in Main and Universe repositories, and it is free for up to five machines. Get Ubuntu Pro References CVE-2026-26007 CVE-2026-26007 Related notices USN-8087-1 USN-8087-1