mcdope pam_usb up to 0.9.2 deny_remote src/tmux.c pusb_tmux_has_remote_clients incorrect regex

Summaryinfo

A vulnerability, which was classified as problematic, was found in mcdope pam_usb up to 0.9.2. This impacts the function pusb_tmux_has_remote_clients of the file src/tmux.c of the component deny_remote. Executing a manipulation can lead to incorrect regex. This vulnerability appears as CVE-2026-64668. The attack requires local access. There is no available exploit. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in mcdope pam_usb up to 0.9.2. It has been declared as problematic. This vulnerability affects the function pusb_tmux_has_remote_clients of the file src/tmux.c of the component deny_remote. The manipulation with an unknown input leads to a incorrect regex vulnerability. The CWE definition for the vulnerability is CWE-185. The product specifies a regular expression in a way that causes data to be improperly matched or compared. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability was named CVE-2026-64668 since 07/20/2026. The exploitation appears to be easy. Local access is required to approach this attack. Successful exploitation requires user interaction by the victim. Technical details are known, but there is no available exploit.

Upgrading to version 0.9.3 eliminates this vulnerability.

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Productinfo

Vendor

• mcdope

Name

• pam_usb

Version

• 0.9.0
• 0.9.1
• 0.9.2

Website

• Product: https://github.com/mcdope/pam_usb/

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