CVE-2026-54411

Description

Linux-PAM through 1.7.2 contains an observable timing discrepancy (CWE-208) in the pam_userdb module's plaintext-password comparison path in modules/pam_userdb/pam_userdb.c that allows a local or network-adjacent attacker able to repeatedly drive authentication through a calling service to recover the plaintext password of a target account by measuring response-timing differences. The comparison uses strncmp() (or strncasecmp() when PAM_ICASE_ARG is set) preceded by a length-equality check, so the time to reject a candidate depends on the index of the first differing byte and on whether the candidate's length matches the stored password, leaking the password length and individual prefix bytes. The vulnerable path is reached when the administrator configures pam_userdb with crypt=none, with an unrecognized crypt method, or without a crypt= argument, causing the module to store and compare credentials in plaintext.

How to fix CVE-2026-54411

No fixed version has been published yet. Mitigate by removing the affected package or applying upstream guidance from the references below.

• —no fix listed

Is CVE-2026-54411 being exploited?

Low — EPSS is 0.3%, meaning exploitation activity has not been observed at scale.

Affected packages (1)

• from 0

CVSS scores

References (1)

• ADVISORYsecurity-tracker.debian.org/tracker/CVE-2026-54411