CVE-2023-4421 Information

Description

The NSS code used for checking PKCS1 v1.5 was leaking information useful in mounting Bleichenbacher-like attacks. Both the overall correctness of the padding as well as the length of the encrypted message was leaking through timing side-channel. By sending large number of attacker-selected ciphertexts the attacker would be able to decrypt a previously intercepted PKCS1 v1.5 ciphertext (for example to decrypt a TLS session that used RSA key exchange) or forge a signature using the victim’s key. The issue was fixed by implementing the implicit rejection algorithm in which the NSS returns a deterministic random message in case invalid padding is detected as proposed in the Marvin Attack paper. This vulnerability affects NSS < 3.61.

Reference

https://bugzilla.mozilla.org/show_bug.cgi?id=1651411 https://www.mozilla.org/security/advisories/mfsa2023-53/