pam_usb: Command injection via $TMUX environment variable leads to RCE as root

published 2026-05-27 5mo ago modified 2026-10-26 14d ago also EUVD-2026-32657

cvss: 8.8; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.2%; EPSS 0.2% chance of exploitation in 30 days, percentile 4%
public exploits: 0; none known

pam_usb provides hardware authentication for Linux using ordinary removable media. Prior to 0.8.7, src/tmux.c reads the user's $TMUX environment variable, splits it on commas, and interpolates the socket-path component directly into a shell command passed to popen(). Because the value is placed inside double-quotes without sanitisation, any value containing " terminates the quoted string and injects arbitrary shell syntax. popen() runs as root inside the PAM stack. This vulnerability is fixed in 0.8.7.

Is CVE-2026-44713 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: total
Assessed: 5mo ago (2026-05-30)

Exploit prediction

0.16% chance of exploitation in the next 30 days, higher than 4% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
CNA	3.1	8.8	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Affected products

mcdope pam_usb

Classification

Weakness

CWE-78 Improper Neutralization of Special Elements used in an OS Command
CWE-116 Improper Encoding or Escaping of Output

References

github.com /mcdope/pam_usb/security/advisories/GHSA-822m-whrh-vrj8

Sources

CVE List CVE-2026-44713
NVD CVE-2026-44713

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.