Yubico PAM Module before 2.10 performed user authentication when 'use_first_pass' PAM configuration option was not used and the module was…

published 2019-11-26 6 y ago modified 2026-06-16 4 mo ago also EUVD-2011-4068

cvss: 9.8; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 2.0%; EPSS 2.0% chance of exploitation in 30 days, percentile 81%
public exploits: 0; none known

Yubico PAM Module before 2.10 performed user authentication when 'use_first_pass' PAM configuration option was not used and the module was configured as 'sufficient' in the PAM configuration. A remote attacker could use this flaw to circumvent common authentication process and obtain access to the account in question by providing a NULL value (pressing Ctrl-D keyboard sequence) as the password string.

Patch / fix

fixed in 1 distros 1 links 1

yubico pam_module 2.10

yubico-pam Debian 14, Debian 13, Debian 12 2.10-1

debian advisories DEBIAN-CVE-2011-4120

bugzilla.redhat.com/show_bug.cgi?id=CVE-2011-4120 advisory

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2011-4120 updated 2025-11-21 cvss 4.0

pam_yubico: Authentication bypass via NULL password

Red Hat All currently supported Red Hat products
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

2.02% chance of exploitation in the next 30 days, higher than 81% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
NVD	3.1	9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD	2.0	7.5	AV:N/AC:L/Au:N/C:P/I:P/A:P

Affected products

yubico-pam yubico-pam

Classification

Weakness

CWE-20 Improper Input Validation

References

bugzilla.redhat.com /show_bug.cgi?id=CVE-2011-4120
issue-tracking, patch, third-party-advisory
security-tracker.debian.org /tracker/CVE-2011-4120
third-party-advisory
access.redhat.com /security/cve/cve-2011-4120
broken-link, third-party-advisory
openwall.com /lists/oss-security/2011/11/07/6
mailing-list, third-party-advisory

Sources

CVE List CVE-2011-4120
NVD CVE-2011-4120

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary