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OS Command InjectionWeakness · CWE-78

CVE-2026-44713

HIGH · 8.8 CVSS v3.1 Published 2026-05-27
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
90/100
Remediation priority · Urgent
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

pam_usb before 0.8.7 has a command injection vulnerability in src/tmux.c. The $TMUX environment variable is read, split on commas, and the socket-path component is directly interpolated into a shell command passed to popen() without sanitization. Since the value is placed inside double-quotes, a malicious value containing a double-quote character can escape the quoted string and inject arbitrary shell syntax. Because popen() executes inside the PAM stack, this runs as root, enabling privilege escalation.

MitigationUpgrade to pam_usb version 0.8.7 or later. As a workaround, unset or strictly control the TMUX environment variable for processes using PAM authentication until the upgrade is applied.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify if pam_usb PAM module is installed
    Search for the pam_usb shared object in common PAM module directories (e.g., ls /lib/security/pam_usb.so, /lib64/security/pam_usb.so, or check your distribution's PAM module path)
    Affected if The pam_usb.so file exists in the PAM module directory
  2. Determine installed pam_usb version
    Run 'pam_usb --version' or check the package manager (dpkg -l | grep pam-usb, rpm -q pam-usb, etc.) to retrieve the version number
    Affected if The installed version is earlier than 0.8.7 (e.g., 0.8.6, 0.8.5, etc.)
  3. Check if TMUX environment variable is present
    Inspect environment variables for TMUX by running 'echo $TMUX' in user sessions or checking process environments of services using PAM authentication (e.g., login, sshd, sudo)
    Affected if The TMUX environment variable is set and contains a value that could be controlled by a user
  4. Verify pam_usb is loaded in PAM configuration
    Examine PAM configuration files (e.g., /etc/pam.d/common-auth, /etc/pam.d/system-auth, or service-specific files like /etc/pam.d/sshd) for lines containing 'pam_usb'
    Affected if pam_usb is configured as an authentication module in any PAM stack that handles privileged operations

A user is affected if pam_usb earlier than version 0.8.7 is installed, loaded in a PAM stack, and the TMUX environment variable is present in contexts where that PAM stack is invoked, allowing command injection as root.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade to pam_usb version 0.8.7 or later. As a workaround, unset or strictly control the TMUX environment variable for processes using PAM authentication until the upgrade is applied.

Recommended fix High confidence

0.8.7

  1. 1. Identify the currently installed pam_usb version using your system's package manager (e.g., dpkg -l | grep pam-usb, rpm -qa | grep pam-usb, or check source code version)
  2. 2. Obtain pam_usb version 0.8.7 or later from the official source (GitHub releases or distribution package repository)
  3. 3. Back up the current pam_usb configuration files (typically in /etc/pam_usb/ or as specified in your setup)
  4. 4. Upgrade pam_usb to version 0.8.7 using your package manager or by compiling from source
  5. 5. Verify the upgrade was successful by checking the installed version matches 0.8.7 or later
  6. 6. Test that the PAM authentication still functions correctly with your hardware token

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing4.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,900
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-44713 in production — separate from our analysis above.

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