Bug 2496416

Summary:	CVE-2026-54411 pam: Plaintext password recovery via timing discrepancy in pam_userdb module [fedora-all]
Product:	[Fedora] Fedora	Reporter:	Michal Findra <mfindra>
Component:	pam	Assignee:	Iker Pedrosa <ipedrosa>
Status:	CLOSED ERRATA	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	medium	Docs Contact:
Priority:	medium
Version:	rawhide	CC:	besser82, ipedrosa, tm
Target Milestone:	---	Keywords:	Security, SecurityTracking
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:	{"flaws": ["400814e8-ad4d-40c4-82ce-be9f07360b42"]}
Fixed In Version:	pam-1.7.2-2.fc44 pam-1.7.1-5.fc43	Doc Type:	---
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2026-07-10 00:53:18 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	2488766

Description Michal Findra 2026-07-02 09:37:46 UTC

Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.

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.

Comment 1 Fedora Update System 2026-07-08 08:02:40 UTC

FEDORA-2026-377015b34b (pam-1.7.2-2.fc44) has been submitted as an update to Fedora 44.
https://bodhi.fedoraproject.org/updates/FEDORA-2026-377015b34b

Comment 2 Fedora Update System 2026-07-09 01:45:25 UTC

FEDORA-2026-377015b34b has been pushed to the Fedora 44 testing repository.
Soon you'll be able to install the update with the following command:
`sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2026-377015b34b`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2026-377015b34b

See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.

Comment 3 Fedora Update System 2026-07-10 00:53:18 UTC

FEDORA-2026-377015b34b (pam-1.7.2-2.fc44) has been pushed to the Fedora 44 stable repository.
If problem still persists, please make note of it in this bug report.

Comment 4 Fedora Update System 2026-07-10 08:15:21 UTC

FEDORA-2026-adc8ddbeaa (pam-1.7.1-5.fc43) has been submitted as an update to Fedora 43.
https://bodhi.fedoraproject.org/updates/FEDORA-2026-adc8ddbeaa

Comment 5 Fedora Update System 2026-07-11 01:46:47 UTC

FEDORA-2026-adc8ddbeaa has been pushed to the Fedora 43 testing repository.
Soon you'll be able to install the update with the following command:
`sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2026-adc8ddbeaa`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2026-adc8ddbeaa

See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.

Comment 6 Fedora Update System 2026-07-26 01:16:06 UTC

FEDORA-2026-adc8ddbeaa (pam-1.7.1-5.fc43) has been pushed to the Fedora 43 stable repository.
If problem still persists, please make note of it in this bug report.