CVE-2026-64668

CVSS 7.4 (high) · published 2026-11-11

pam_usb provides hardware authentication for Linux using removable media. From version 0.8.0 to before version 0.9.3, the deny_remote feature in pam_usb uses /usr/bin/w -i to detect whether the authenticating user has an active remote tmux session. In pusb_tmux_has_remote_clients() (src/tmux.c), the IPv6 detection pattern matched the address group and then immediately expected whitespace. On Linux systems with multi-homed network interfaces, w -i appends a zone index (scope identifier) to link-local IPv6 addresses — e.g. fe80::1%eth0. The %eth0 suffix appeared between the address and the next whitespace field, causing the regex match to fail even for an otherwise-matching remote session. The function returned "no remote clients" and granted access. This issue has been patched in version 0.9.3.

Weakness: CWE-285, CWE-693

Source: NVD CVE-2026-64668

References

• https://github.com/mcdope/pam_usb/commit/a62513f3da871d6576d751de3482eb80b9ac79f3
• https://github.com/mcdope/pam_usb/pull/423
• https://github.com/mcdope/pam_usb/releases/tag/0.9.3
• https://github.com/mcdope/pam_usb/security/advisories/GHSA-7583-9cqv-j9rf

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