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VulnerabilityPublished Updated

CVE-2026-48983: mcdope pam_usb · Time-of-check Time-of-use (TOCTOU) Race Condition

Affects mcdope pam_usbSource CVE Database V5

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Not known to be exploited · CVSS 5.8 Medium : upgrade to 0.9.2 when convenient.

Data as of 31 Oct 2026, 20:20 UTC

CVSS 3.1 base score
5.8Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 1% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 0.9.2
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:L

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 18 Jun 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 31 Oct 2026.

What to do

Upgrade pam_usb and mcdope/pam_usb to 0.9.2.

Affected software

ProductAffectedFixed in
mcdopepam_usbAffected
  • <0.9.2
Fixed in
  • 0.9.2
GitHubmcdope/pam_usbpkg:github/mcdope/pam_usbOther threatsAffected
  • <0.9.2
Fixed in
  • 0.9.2

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade pam_usb to version 0.9.2 or later, where this TOCTOU race condition has been fixed. No other mitigation or workaround is indicated.

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.

References

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