USN-8769-1: phpseclib vulnerability

Ubuntu patches phpseclib non-constant-time padding validation enabling remote padding oracle timing attacks against AES-CBC.

Ubuntu security notice USN-8769-1 addresses a vulnerability in phpseclib where padding validation was not performed in constant time when using AES in CBC mode. A remote attacker could leverage this timing side channel to conduct a padding oracle attack and decrypt sensitive information. Users are advised to update the phpseclib package.

• Non-constant-time padding checks in AES-CBC mode expose a timing oracle
• Remote attackers could decrypt sensitive data via padding oracle attack