# CVE-2026-47269: pam_usb: deny_remote feature incorrectly classifies IPv4-mapped IPv6 remote connections as local

> Attackers with physical USB access can bypass remote authentication restrictions on Linux systems using pam_usb with specific IPv6 configurations.

- **Severity:** High 7.4 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 27 May 2026
- **Updated:** 28 May 2026
- **Also known as:** GHSA-jmmj-qhrq-w45g

## What is CVE-2026-47269?

CVE-2026-47269 is a high-severity authentication bypass vulnerability in mcdope pam_usb, published on 27 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

pam_usb provides hardware authentication for Linux using ordinary removable media. Prior to 0.9.0,  pam_usb's deny_remote feature checks utmpx ut_addr_v6 to detect whether an authentication request originates from a remote session. The outer guard was if (utent->ut_addr_v6[0] != 0), which only tests the first 32-bit word of the 128-bit address field. IPv4-mapped IPv6 addresses (::ffff:x.x.x.x) store the IPv4 address in ut_addr_v6[3] with ut_addr_v6[0] == 0. On systems where the SSH daemon listens on :: (IPv6 wildcard) with AddressFamily any -- common on Ubuntu and Debian -- incoming IPv4 connections are recorded in utmpx as IPv4-mapped IPv6 addresses. The outer check evaluates to false, the remote-detection block is skipped entirely, and the session is treated as local. deny_remote=true does not block the authentication. An attacker with physical access to a registered USB device can authenticate over SSH on an affected system as if they were sitting at a local terminal, bypassing the deny_remote restriction. This vulnerability is fixed in 0.9.0.

Weakness: CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2026-47269?


## How do I fix CVE-2026-47269?

No fix has been published for CVE-2026-47269 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-47269 being exploited?

There is no known exploitation of CVE-2026-47269 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-47269 and fix it if it is affected.

What it is: CVE-2026-47269 is a high-severity authentication bypass vulnerability in mcdope pam_usb, published on 27 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-47269 in the wild and no public exploit code.

Affected product: mcdope pam_usb. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-47269/ (Markdown: https://insights.sbomify.com/CVE-2026-47269/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-47269
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-47269
- OSV: https://osv.dev/vulnerability/CVE-2026-47269

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-47269/
Summaries are generated and may contain mistakes; the official description above is the record.