CVE-2026-48066
Deferred Deferred - Pending Action
Race Condition in pam_usb Authentication Module

Publication date: 2026-05-27

Last updated on: 2026-05-27

Assigner: GitHub, Inc.

Description
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.
CVSS Scores
EPSS Scores
Probability:
Percentile:
Meta Information
Published
2026-05-27
Last Modified
2026-05-27
Generated
2026-06-17
AI Q&A
2026-05-27
EPSS Evaluated
2026-06-15
NVD
CVE-2026-48066
Affected Vendors & Products
Showing 2 associated CPEs
Vendor Product Version / Range
mcdope pam_usb to 0.9.1 (exc)
mcdope pam_usb From 0.9.1 (inc)
Helpful Resources
Exploitability
CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-476 The product dereferences a pointer that it expects to be valid but is NULL.
CWE-362 The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
Attack-Flow Graph
AI Quick Actions
Instant insights powered by AI
Impact Analysis

This vulnerability can lead to data races during concurrent PAM invocations, potentially causing unexpected behavior or crashes in the authentication process. The CVSS score indicates a moderate impact with a high impact on availability, meaning it could disrupt authentication services but does not directly compromise confidentiality.

Executive Summary

The vulnerability exists in pam_usb versions prior to 0.9.1, specifically in the src/log.c file. It involves a process-wide static pointer that is overwritten on every PAM invocation with the address of a stack-local variable. This design violates the PAM re-entrancy requirement and causes a data race when multiple threads invoke the PAM stack concurrently.

Mitigation Strategies

To mitigate this vulnerability, upgrade pam_usb to version 0.9.1 or later, where the issue has been fixed.

Compliance Impact

The provided information does not specify any direct impact of the CVE-2026-48066 vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

Detection Guidance

The vulnerability can be detected by checking for data races during concurrent PAM authentication invocations involving pam_usb versions 0.9.0 and earlier.

One suggested method is to build pam_usb with ThreadSanitizer enabled using the compiler flag -fsanitize=thread.

Then, run concurrent invocations of the pamusb-check command to trigger the race condition and observe if ThreadSanitizer reports any data races.

  • Compile pam_usb with ThreadSanitizer: gcc -fsanitize=thread -o pamusb-check src/log.c other_sources.c
  • Run multiple concurrent pamusb-check commands, for example: for i in {1..10}; do ./pamusb-check & done; wait

If data races are detected, ThreadSanitizer will output warnings indicating the presence of the vulnerability.

Chat Assistant
Ask questions about this CVE
Hi! I’m here to help you understand CVE-2026-48066. Ask me anything about the vulnerability, its impact, or mitigation strategies.
0/70
EPSS Chart