mcdope pam_usb up to 0.8.6 on Linux Environment Variable PINENTRY_FALLBACK_APP os command injection

Summaryinfo

A vulnerability was found in mcdope pam_usb up to 0.8.6 on Linux. It has been rated as critical. Affected is an unknown function of the component Environment Variable Handler. This manipulation of the argument PINENTRY_FALLBACK_APP causes os command injection. This vulnerability is handled as CVE-2026-44709. It is possible to launch the attack on the local host. There is not any exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in mcdope pam_usb up to 0.8.6 on Linux. It has been declared as critical. Affected by this vulnerability is an unknown function of the component Environment Variable Handler. The manipulation of the argument PINENTRY_FALLBACK_APP with an unknown input leads to a os command injection vulnerability. The CWE definition for the vulnerability is CWE-78. 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. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-44709 since 05/07/2026. The exploitation appears to be easy. An attack has to be approached locally. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1202 for this issue.

Upgrading to version 0.8.7 eliminates this vulnerability.

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Productinfo

Vendor

• mcdope

Name

• pam_usb

Version

• 0.8.0
• 0.8.1
• 0.8.2
• 0.8.3
• 0.8.4
• 0.8.5
• 0.8.6

Website

• Product: https://github.com/mcdope/pam_usb/

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