CVE-2026-48983
pam_usb: TOCTOU race condition in pad directory creation allows symlink substitution
Description
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.
INFO
Published Date :
June 18, 2026, 7:07 p.m.
Last Modified :
June 18, 2026, 7:07 p.m.
Remotely Exploit :
No
Source :
GitHub_M
Affected Products
The following products are affected by CVE-2026-48983
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
Solution
- Update pam_usb to version 0.9.2 or later.
- Remove any existing symlinks in pad directories.
- Verify pad files are created securely.
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