Vulnerability · Published Dec 12, 2023 · Assigned by mozilla
CVE-2023-4421
Medium 6.5
In plain English
A medium-severity security flaw in NSS from Mozilla. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.8% (higher than 56% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | nss | 2:3.61-1 | DEBIAN-CVE-2023-4421 |
| Debian:13 | nss | 2:3.61-1 | DEBIAN-CVE-2023-4421 |
| Debian:14 | nss | 2:3.61-1 | DEBIAN-CVE-2023-4421 |
| Ubuntu:22.04:LTS | nss | 2:3.98-0ubuntu0.22.04.1 | USN-6727-1 |