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.

• CWE-203

• https://bugzilla.mozilla.org/show_bug.cgi?id=1651411Issue Tracking
• https://www.mozilla.org/security/advisories/mfsa2023-53/Issue Tracking, Vendor Advisory
• https://bugzilla.mozilla.org/show_bug.cgi?id=1651411Issue Tracking
• https://lists.debian.org/debian-lts-announce/2023/10/msg00039.html
• https://www.mozilla.org/security/advisories/mfsa2023-53/Issue Tracking, Vendor Advisory

Published

Dec 12, 2023

Last Modified

Jun 17, 2026

Status

Modified

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