---
id: "CVE-2026-64668"
page: "https://infrastack.ai/live/CVE-2026-64668"
kind: "vulnerability"
aliases: ["CVE-2026-64668"]
title: "pam_usb: remote-session check fails open on IPv6 zone-indexed addresses"
severity: "high"
cvss: 7.4
epss: null
exploited: false
status: "open"
category: "other"
products: [{"name": "pam_usb", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["ipv6", "linux", "other", "pam", "pam-usb", "ssh", "tmux"]
not_affected_if: ["deny-remote-disabled", "no-ipv6-remote-sessions", "version-0.9.3-or-later"]
published_at: "2026-11-11T05:19:51+00:00"
first_seen_at: "2026-11-11T05:25:39+00:00"
updated_at: "2026-11-11T05:26:44+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64668", "first_seen_at": "2026-11-11T05:25:39+00:00"}]
exploit_sources: []
---

# pam_usb: remote-session check fails open on IPv6 zone-indexed addresses

Link for people: https://infrastack.ai/live/CVE-2026-64668 (this .md is for agents)

pam_usb's deny_remote check misses remote tmux sessions whose link-local IPv6 address carries a zone index such as %eth0. When the match fails, the module reports no remote clients and grants access that deny_remote should block.

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

## Affected

- vendor:pam_usb affected range not listed fixed no fixed version listed

## How to check

- Confirm the installed pam_usb version is `0.8.0` or later but before `0.9.3`.
- Check whether the `deny_remote` feature is enabled in your pam_usb configuration.
- Look for multi-homed Linux hosts with link-local IPv6 addresses that have tmux sessions open.

## Fix

- Upgrade pam_usb to `0.9.3` or later.

## Timeline

- 2026-11-11T05:25:39+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-64668

## Documents

- [advisory] Vendor advisory: github.com https://github.com/mcdope/pam_usb/security/advisories/GHSA-7583-9cqv-j9rf
- [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 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.

---

_Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai_