Observable Discrepancy

Summary

A timing-based side channel exists in the OpenSSL versions 1.0.2-beta1 through 1.0.2u, 1.1.1-pre1 through 1.1.1s, and 3.0.0-alpha1 through 3.0.7. RSA Decryption implementation which could be sufficient to recover 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.