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Improper AuthenticationWeakness · CWE-287

CVE-2026-47272

HIGH · 7.1 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 →
73/100
Remediation priority · Elevated
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 0.9.0, the pusb_pad_compare() function in src/pad.c only verified that the user-side pad (~/.pamusb/device.pad) could be read, but did not enforce that the system-side pad (the pad file on the USB device) was also present and readable. If the user-side pad was deleted or unreadable, the function returned a failure that was treated as non-fatal in certain code paths, allowing authentication to succeed without the USB device being verified. A local user can delete their own ~/.pamusb/device.pad to remove the USB device requirement and authenticate without the physical device. This vulnerability is fixed in 0.9.0.

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 versions before 0.9.0 have an authentication bypass vulnerability in the pusb_pad_compare() function in src/pad.c. The function only validated that the user-side pad file (~/.pamusb/device.pad) was readable but failed to enforce that the system-side pad on the physical USB device was also present and accessible. When the user-side pad was deleted or unreadable, certain code paths treated this as a non-fatal error, allowing authentication to succeed without the required USB hardware token.

MitigationUpgrade pam_usb to version 0.9.0 or later, which enforces verification of both user-side and system-side pad files. Alternatively, ensure ~/.pamusb/device.pad files are protected and not deletable by end users.

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
Unchanged
Confidentiality
High
Integrity
High
Availability
None

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

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 is installed
    Check for pam_usb package using your package manager (e.g., dpkg -l | grep pam_usb, rpm -qa | grep pam_usb, or which pusb_pad_compare)
    Affected if pam_usb is installed and version is below 0.9.0
  2. Determine installed pam_usb version
    Run version check command for pam_usb (e.g., pam_usb --version, dpkg -s pam-usb, or check /usr/lib/security/pam_usb.so for version metadata)
    Affected if Version returned is lower than 0.9.0 or version cannot be determined (indicating pre-0.9.0 build)
  3. Check if pam_usb is configured in PAM stack
    Examine PAM configuration files in /etc/pam.d/ (common files: system-auth, password-auth, login, sshd, sudo) and /etc/pam.conf for lines containing 'pam_usb' or 'pamusb.so'
    Affected if pam_usb is present in any PAM configuration file used by authentication services
  4. Verify user-side pad file location
    Check if ~/.pamusb/device.pad exists and is readable by the target user (ls -la ~/.pamusb/device.pad)
    Affected if The pad file exists but the vulnerability allows bypass when this file is deleted or unreadable while authentication proceeds anyway

You are affected if pam_usb version is below 0.9.0 AND pam_usb is configured in your PAM authentication stack, allowing authentication to succeed without the physical USB token when the user-side pad file is missing or inaccessible.

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 pam_usb to version 0.9.0 or later, which enforces verification of both user-side and system-side pad files. Alternatively, ensure ~/.pamusb/device.pad files are protected and not deletable by end users.

Recommended fix High confidence

0.9.0

  1. 1. Check the currently installed version of pam_usb (e.g., via package manager or by querying the installed package)
  2. 2. Obtain pam_usb version 0.9.0 or later from the project's GitHub repository or official distribution channels
  3. 3. Upgrade pam_usb to version 0.9.0 or newer using the appropriate package manager or build process
  4. 4. Verify the installed version is 0.9.0 or later
  5. 5. Test that hardware authentication with USB devices functions correctly after the upgrade

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

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,060
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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-2026-47272 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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