---
id: "CVE-2026-64669"
page: "https://infrastack.ai/live/CVE-2026-64669"
kind: "vulnerability"
aliases: ["CVE-2026-64669"]
title: "pam_usb: deny_remote check misses remote tmux users on compressed IPv6"
severity: "high"
cvss: 7.4
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["ipv6", "linux", "package", "pam", "pam-usb", "tmux"]
not_affected_if: ["default-config", "pam-usb-0.9.3-or-later", "pam-usb-below-0.8.0"]
published_at: "2026-11-11T05:19:51+00:00"
first_seen_at: "2026-11-11T05:25:40+00:00"
updated_at: "2026-11-11T05:26:35+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64669", "first_seen_at": "2026-11-11T05:25:40+00:00"}]
exploit_sources: []
---

# pam_usb: deny_remote check misses remote tmux users on compressed IPv6

Link for people: https://infrastack.ai/live/CVE-2026-64669 (this .md is for agents)

pam_usb's deny_remote setting is meant to block hardware-key login when the user has a remote tmux session, but its IPv6 parser only recognizes fully written addresses. A remote tmux client connecting from a compressed IPv6 address such as ::1 or 2001:db8::1 goes undetected, so the check reports no remote clients.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed pam_usb version and whether it is between `0.8.0` and `0.9.3`.
- Look for `deny_remote` enabled in the pam_usb configuration (`/etc/security/pam_usb.conf`).
- Check whether users run tmux sessions that accept remote clients over IPv6.

## Fix

- pam_usb: upgrade to `0.9.3` or later.

## Timeline

- 2026-11-11T05:25:40+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-64669

## Documents

- [advisory] Vendor advisory: github.com https://github.com/mcdope/pam_usb/security/advisories/GHSA-gc4c-v52c-2v34
- [fix] Patch: github.com https://github.com/mcdope/pam_usb/commit/a62513f3da871d6576d751de3482eb80b9ac79f3
- [fix] Release notes: github.com https://github.com/mcdope/pam_usb/releases/tag/0.9.3

## From the sources

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.

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