CVE-2026-48981
MediumCVSS 6.7Summary
In versions prior to 0.9.2, pam_usb calls xmlReadFile() with flags=0 when loading the configuration file, allowing libxml2 to process external entity references (XXE). This can lead to outbound network connections or local file reads at XML parse time from the context of the authenticating process.
Risk Assessment
Exploitation requires modification of the configuration file, which limits direct exploitation; however, the defense-in-depth impact is significant since pam_usb.so runs in setuid contexts (sudo, su).
Recommendation
It is recommended to upgrade to version 0.9.2 or later to mitigate this vulnerability. Additionally, access to the pam_usb.conf configuration file should be restricted.
Original NVD description (English source)
pam_usb provides hardware authentication for Linux using ordinary removable media. In versions prior to 0.9.2, pam_usb calls xmlReadFile() with flags=0 when loading the configuration file, allowing libxml2 to process external entity references (XXE), potentially making outbound network connections or local file reads at XML parse time from the context of the authenticating process. The vulnerability requires the configuration file to contain crafted XML entity references. Since pam_usb.conf is root-owned, direct exploitation requires prior write access to the config, but the defence-in-depth impact is significant given that pam_usb.so runs in setuid contexts (sudo, su). This issue has been fixed in version 0.9.2.