Information Exposure Affecting openssl package, versions <3.0.5-2ubuntu2.1

Note: Versions mentioned in the description apply only to the upstream openssl package and not the openssl package as distributed by Ubuntu. See How to fix? for Ubuntu:22.10 relevant fixed versions and status.

A timing based side channel exists in the OpenSSL RSA Decryption implementation which could be sufficient to recover a plaintext across a network in a Bleichenbacher style attack. To achieve a successful decryption an attacker would have to be able to send a very large number of trial messages for decryption. The vulnerability affects all RSA padding modes: PKCS#1 v1.5, RSA-OEAP and RSASVE.

For example, in a TLS connection, RSA is commonly used by a client to send an encrypted pre-master secret to the server. An attacker that had observed a genuine connection between a client and a server could use this flaw to send trial messages to the server and record the time taken to process them. After a sufficiently large number of messages the attacker could recover the pre-master secret used for the original connection and thus be able to decrypt the application data sent over that connection.

• http://people.ubuntu.com/~ubuntu-security/cve/CVE-2022-4304
• https://www.openssl.org/news/secadv/20230207.txt
• https://security.gentoo.org/glsa/202402-08