CVE-2026-64669— pam_usb: deny_remote bypassed by compressed IPv6 addresses in pusb_tmux_has_remote_clients

Quick assessment

Affected

mcdope pam_usb

Exploitation

No confirmed in-the-wild exploitation; assess based on exposure

Recommended action

Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

pam_usb 利用可移动存储介质为 Linux 系统提供硬件认证功能。在从 0.8.0 版本到 0.9.3 版本之前的版本中，pam_usb 的功能通过调用来检测当前认证用户是否存在活跃的远程 tmux 会话。在文件的函数中，用于检测 IPv6 地址的正则表达式严格要求匹配由四个显式冒号分隔的、每组包含 1 到 4 位十六进制数字的格式（例如：）。因此，任何采用压缩表示法的 IPv6 地址——包括回环地址（）、链路本地地址（）以及全局单播地址（）——均无法匹配该模式。这导致远程客户端检查在存在从此

CVSS 7.4 · High Updated Nov 11, 2026

Possible ATT&CK Techniques 2 AI

T1548 · Abuse Elevation Control Mechanism T1190 · Exploit Public-Facing Application

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Vulnerability Information

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Vulnerability Title

pam_usb: deny_remote bypassed by compressed IPv6 addresses in pusb_tmux_has_remote_clients

Source: CVE Program / CVE List V5

Vulnerability Description

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 regex required exactly four explicit colon-separated groups of 1-4 hex digits (e.g. 2001:0db8:85a3:0000). Any IPv6 address in compressed notation — including loopback (::1), link-local (fe80::1), and global unicast addresses (2001:db8::1) — did not match this pattern. As a result the remote-client check silently returned "no remote clients" even when a remote tmux client was connected from such an address. This issue has been patched in version 0.9.3.

Source: CVE Program / CVE List V5

CVSS Information

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Source: CVE Program / CVE List V5

Vulnerability Type

授权机制不恰当

Source: CVE Program / CVE List V5

Affected Products

Vendor	Product	Affected Versions	CPE	Subscribe
mcdope	pam_usb	>= 0.8.0, < 0.9.3	-

II. Public POCs for CVE-2026-64669

#	POC Description	Source Link	Shenlong Link

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III. Intelligence Information for CVE-2026-64669

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Other References for CVE-2026-64669 (4)

https://github.com/mcdope/pam_usb/pull/423 x_refsource_MISC
https://github.com/mcdope/pam_usb/releases/tag/0.9.3 x_refsource_MISC
https://github.com/mcdope/pam_usb/security/advisories/GHSA-gc4c-v52c-2v34 x_refsource_CONFIRM
https://github.com/mcdope/pam_usb/commit/a62513f3da871d6576d751de3482eb80b9ac79f3 x_refsource_MISC

https://www.cve.org/CVERecord?id=CVE-2026-64669

Same Patch Batch · mcdope · 2026-11-11 · 4 CVEs total

CVE-2026-64668	7.4 HIGH	pam_usb: deny_remote bypassed by zone-indexed IPv6 addresses (fe80::1%eth0) in pusb_tmux_h
CVE-2026-64666	7.1 HIGH	pam_usb: getenv() in pusb_local_login bypasses XRDP deny via env-var unset
CVE-2026-64667	4.4 MEDIUM	pam_usb: Heap out-of-bounds read in pusb_get_tty_from_display_server cmdline scan

IV. Related Vulnerabilities

Same product: pam_usb

Same vendor: mcdope

Same weakness: CWE-285