Information Exposure Affecting nss package, versions <2:3.98-0ubuntu0.20.04.1


Severity

Recommended
0.0
medium
0
10

Based on Ubuntu security rating.

Threat Intelligence

EPSS
0.06% (30th percentile)

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  • Snyk IDSNYK-UBUNTU2004-NSS-5921933
  • published27 Sept 2023
  • disclosed12 Dec 2023

Introduced: 27 Sep 2023

CVE-2023-4421  (opens in a new tab)
CWE-203  (opens in a new tab)

How to fix?

Upgrade Ubuntu:20.04 nss to version 2:3.98-0ubuntu0.20.04.1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream nss package and not the nss package as distributed by Ubuntu. See How to fix? for Ubuntu:20.04 relevant fixed versions and status.

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.

CVSS Scores

version 3.1