CVE-2026-48983 — pam_usb: TOCTOU race condition in pad directory creation allows symlink substitution
pam_usb provides hardware authentication for Linux using ordinary removable media. In versions prior to 0.9.2, a symlink race condition exists in per-device and per-user pad dir…
Published: 2026-06-18 · CVSS: 5.8 · CVSS 3.1
pam_usb provides hardware authentication for Linux using ordinary removable media. In versions prior to 0.9.2, a symlink race condition exists in per-device and per-user pad directory creation. pam_usb uses a check-then-act pattern: it calls lstat() to test for existence and then calls mkdir() separately to create the directory. A local attacker can win the race between these calls by replacing the target path with a symlink to a directory they control. If successful, one-time pad files may be written to an attacker-controlled location, potentially exposing future pad values before use or disrupting authentication. This issue has been fixed in version 0.9.2.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7