PatchSiren cyber security CVE debrief
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.
Official resources
2026-05-27