CVE-2026-44709: pam_usb: PINENTRY_FALLBACK_APP environment variable allows arbitrary command execution

Vulnerability summary

CVE-2026-44709 is a high (CVSS 7.8) OS Command Injection vulnerability in mcdope pam_usb. EPSS estimates a 0.21% chance of exploitation in the next 30 days, higher than 10.7% of scored vulnerabilities.

Timeline

1. 27-05-2026
   PublishedVulnerability first disclosed.
2. 02-06-2026
   Last modifiedVulnerability information updated.

Description

pam_usb provides hardware authentication for Linux using ordinary removable media. Prior to 0.8.7, pamusb-pinentry reads the PINENTRY_FALLBACK_APP environment variable and executes it directly without any validation. Any process that can set environment variables before pamusb-pinentry is invoked can point PINENTRY_FALLBACK_APP at an arbitrary binary or script and have it executed with the privileges of the pam_usb tool chain. This vulnerability is fixed in 0.8.7.

• CWE-78Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.