CVE-2023-4421

The NSS code used for checking PKCS#1 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
PKCS#1 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.

Bugs

• <https://bugzilla.redhat.com/show_bug.cgi?id=2238677&gt;
• <https://bugzilla.mozilla.org/show_bug.cgi?id=1651411&gt;

Notes