PT-2026-49134 · Linux Pam · Linux-Pam

Xurshidbek Sobirjonov · Published 2026-06-14 · Updated 2026-06-14 · CVE-2026-54411

Mitre

CVSS v3.1

5.9

Medium

Base vector

AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

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.

Fix

Weakness Enumeration

CWE-208

Related Identifiers

CVE-2026-54411

Affected Products

Linux-Pam

References · 5

• https://nvd.nist.gov/vuln/detail/CVE-2026-54411 · Security Note
• https://github.com/linux-pam/linux-pam · Note
• https://cwe.mitre.org/data/definitions/208.html · Note
• https://github.com/linux-pam/linux-pam/blob/master/modules/pam_userdb/pam_userdb.c#L327 · Note
• https://github.com/linux-pam/linux-pam/blob/master/libpam/include/pam_inline.h · Note