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.
CVSS Vector Breakdown
AV:LAttack VectorAC:HAttack ComplexityPR:LPrivileges RequiredUI:NUser InteractionS:UScopeC:HConfidentialityI:LIntegrityA:LAvailabilityWeaknesses
Affected Products
Attack Graph
Click technique nodes to view MITRE ATT&CK details. Scroll to zoom, drag to pan.
Exploitability
MITRE ATT&CK
1 techniqueReferences
Timeline
Unlock Complete Vulnerability Intelligence
Get the full picture for CVE-2026-48983 and every CVE in our database. Create a free account — no credit card required.
Create Free Account