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CVE-2026-47274 mcdope CVE debrief

pam_usb prior to 0.9.0 resolves external binaries through PATH rather than absolute paths in multiple helper tools, allowing environment-influenced binary substitution during PAM authentication. The affected components are pamusb-check (src/tmux.c), pamusb-conf (tools/pamusb-conf), and pamusb-keyring-unlock-gnome (tools/pamusb-keyring-unlock-gnome). An attacker with ability to manipulate the process environment during authentication or tool execution could redirect execution to malicious binaries. This vulnerability is classified as CWE-427 (Uncontrolled Search Path Element). The issue was fixed in version 0.9.0 through commits addressing path resolution in each affected tool.

Vendor
mcdope
Product
pam_usb
CVSS
MEDIUM 6.3
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-27
Original CVE updated
2026-05-28
Advisory published
2026-05-27
Advisory updated
2026-05-28

Who should care

Linux system administrators using pam_usb for hardware-based authentication; security teams managing PAM configurations; organizations relying on removable media for multi-factor authentication on Linux systems

Technical summary

The pam_usb library provides hardware authentication for Linux using removable media. Multiple helper tools in versions prior to 0.9.0 used relative binary resolution through the PATH environment variable instead of absolute paths. The affected tools—pamusb-check, pamusb-conf, and pamusb-keyring-unlock-gnome—could be redirected to attacker-controlled binaries when the process environment is manipulated. This represents an uncontrolled search path element vulnerability (CWE-427). The fix in 0.9.0 replaces PATH-dependent resolution with absolute paths in all three components.

Defensive priority

medium

Recommended defensive actions

  • Upgrade pam_usb to version 0.9.0 or later to obtain fixes for PATH-dependent binary resolution
  • Audit PAM configuration to ensure pam_usb is updated across all authentication paths
  • Review environment variable controls for PAM authentication processes to limit PATH manipulation opportunities
  • Monitor for unauthorized modifications to directories in default PATH locations that could be used for binary substitution
  • Verify integrity of pamusb-check, pamusb-conf, and pamusb-keyring-unlock-gnome binaries after update

Evidence notes

Official CVE record published 2026-05-27. GitHub Security Advisory GHSA-pp29-w28g-r9h9 confirms affected versions and fix. Three commits (1ee87459, 52a1fd64, 993e73d8) implement the fix by using absolute paths instead of PATH-dependent resolution. CVSS 3.1 vector AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N indicates local attack vector with high attack complexity, requiring low privileges but no user interaction, with high impact to confidentiality and integrity.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-47274 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-47274

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-47274 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-47274

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.