CVE-2026-48983 json
pam_usb: TOCTOU race condition in pad directory creation allows symlink substitution
published 2026-06-18 4 mo ago modified 2026-10-26 14 d ago also EUVD-2026-37936
- cvss
- 5.8
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.1%
- EPSS 0.1% chance of exploitation in 30 days, percentile 1%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 4 mo ago
Exploit prediction
0.11% chance of exploitation in the next 30 days, higher than 1% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 5.8 | CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:L |
Affected products
- mcdope pam_usb
Classification
- Weakness
-
- CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition
References
Sources
- CVE List CVE-2026-48983
- NVD CVE-2026-48983
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