# CVE-2026-64666: pam_usb: getenv() in pusb_local_login bypasses XRDP deny via env-var unset

Status: published. Published: 2026-11-11. Updated: 2026-11-11.

pam_usb provides hardware authentication for Linux using removable media. Prior to version 0.9.3, src/local.c reads XRDP_SESSION with plain getenv(3) at the head of pusb_local_login while every other env consumer in the same function uses secure_getenv(3). When pam_usb.so loads into a setuid PAM host, the calling user controls the environment passed in. Clearing XRDP_SESSION before invoking the host bypasses the explicit XRDP-deny rule. Other remote-detection signals (rmsvc, evdev, loginctl, utmp) may still catch the session, but the env-based detection alone is defeated. This issue has been patched in version 0.9.3.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- mcdope / pam_usb: < 0.9.3 (affected). Source: CNA: GitHub_M

## Severity and prioritization

- CVSS 3.1: 7.1 (high); CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-807

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/mcdope/pam_usb/security/advisories/GHSA-ffx6-xjp6-x33g (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/mcdope/pam_usb/issues/410 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/mcdope/pam_usb/pull/417 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/mcdope/pam_usb/commit/0b179ed679d6522c6a571c5a8ae9bdc7edbad31f (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/mcdope/pam_usb/releases/tag/0.9.3 (CNA: GitHub_M; x_refsource_MISC)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-64666; retrieved 2026-11-11; source updated 2026-11-11

Revision: 386ad73f440855b5205d7a9917687bf2ee3f9b85f5ca67d60f73a8bec9eccc1b

Canonical: https://y2.dev/cve/CVE-2026-64666

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