CVE-2026-64668— pam_usb: deny_remote bypassed by zone-indexed IPv6 addresses (fe80::1%eth0) 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 系统提供硬件身份验证。在版本 0.8.0 至 0.9.3 之前，pam_usb 的功能通过调用来检测正在认证的用户是否拥有活跃的远程 tmux 会话。在函数（位于）中，IPv6 地址检测模式在匹配地址组后，立即期望出现空白字符。然而，在拥有多宿主网络接口的 Linux 系统上，命令会在链路本地 IPv6 地址后附加区域索引（作用域标识符），例如。后缀出现在地址与下一个空白字段之间，导致正则表达式匹配失败，即使该会话实际上符合远程会话的特征。因此，该函数

CVSS 7.4 · High Updated Nov 11, 2026

Possible ATT&CK Techniques 2 AI

T1078 · Valid Accounts T1190 · Exploit Public-Facing Application

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Vulnerability Information

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Vulnerability Title

pam_usb: deny_remote bypassed by zone-indexed IPv6 addresses (fe80::1%eth0) 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 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.

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-2026-64668

#	POC Description	Source Link	Shenlong Link

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III. Intelligence Information for CVE-2026-64668

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Other References for CVE-2026-64668 (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-7583-9cqv-j9rf x_refsource_CONFIRM
https://github.com/mcdope/pam_usb/commit/a62513f3da871d6576d751de3482eb80b9ac79f3 x_refsource_MISC

https://www.cve.org/CVERecord?id=CVE-2026-64668

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

CVE-2026-64669	7.4 HIGH	pam_usb: deny_remote bypassed by compressed IPv6 addresses in pusb_tmux_has_remote_clients
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