pam_usb: Thread-unsafe static pointer in log.c causes data race under concurrent PAM authentication

published 2026-05-27 5 mo ago modified 2026-10-26 14 d ago also EUVD-2026-32648

cvss: 5.7; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.1%; EPSS 0.1% chance of exploitation in 30 days, percentile 1%
public exploits: 0; none known

pam_usb provides hardware authentication for Linux using ordinary removable media. Prior to 0.9.1, src/log.c contains a process-wide static pointer that is written on every PAM invocation with the address of a stack-local variable. This violates the PAM re-entrancy requirement and creates a data race when the PAM stack is invoked concurrently from multiple threads. This vulnerability is fixed in 0.9.1.

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 5 mo ago (2026-05-28)

Exploit prediction

0.12% chance of exploitation in the next 30 days, higher than 1% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	5.7	CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H

Affected products

mcdope pam_usb

Classification

Weakness

CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization
CWE-476 NULL Pointer Dereference

References

Sources

CVE List CVE-2026-48066
NVD CVE-2026-48066

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Summary