libnss3: The NSS code used for checking PKCS#1 v1.5 was leaking information useful in mounting Bleichenbacher-like attacks
CVE-2023-4421 is fixed in 3 products on 1 platform, first by DEBIAN-CVE-2023-4421, released December 12, 2023. It is not reported as exploited. Patch Radar priority: Routine.
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.
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Linux | |||
| libnss3 · Ubuntu 20.04 LTS (focal) | 2:3.98-0ubuntu0.20.04.1 | libnss3 2:3.98-0ubuntu0.20.04.1 | Dec 19, 2023 |
| libnss3-tools · Ubuntu 20.04 LTS (focal) | 2:3.98-0ubuntu0.20.04.1 | libnss3-tools 2:3.98-0ubuntu0.20.04.1 | Dec 19, 2023 |
| nss · Debian 12.15 (bookworm) | 2:3.61-1 | DEBIAN-CVE-2023-4421 | Dec 12, 2023 |
| nss · Debian 13.5 (trixie) | 2:3.61-1 | DEBIAN-CVE-2023-4421 | Dec 12, 2023 |
| nss · Debian 14 | 2:3.61-1 | DEBIAN-CVE-2023-4421 | Dec 12, 2023 |
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