# CVE-2026-47272: pam_usb: OTP pad authentication bypass via missing system pad check and uninitialized RNG buffer

> A local attacker can bypass USB hardware authentication by deleting their user-side pad file, allowing login without the physical device.

- **Severity:** High 7.1 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 27 May 2026
- **Updated:** 28 May 2026
- **Also known as:** GHSA-vx6f-rrqr-j87c

## What is CVE-2026-47272?

CVE-2026-47272 is a high-severity authentication bypass vulnerability in mcdope pam_usb, published on 27 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

pam_usb provides hardware authentication for Linux using ordinary removable media. Prior to 0.9.0, the pusb_pad_compare() function in src/pad.c only verified that the user-side pad (~/.pamusb/device.pad) could be read, but did not enforce that the system-side pad (the pad file on the USB device) was also present and readable. If the user-side pad was deleted or unreadable, the function returned a failure that was treated as non-fatal in certain code paths, allowing authentication to succeed without the USB device being verified. A local user can delete their own ~/.pamusb/device.pad to remove the USB device requirement and authenticate without the physical device. This vulnerability is fixed in 0.9.0.

Weakness: CWE-908 (Use of Uninitialized Resource), CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2026-47272?


## How do I fix CVE-2026-47272?

No fix has been published for CVE-2026-47272 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-47272 being exploited?

There is no known exploitation of CVE-2026-47272 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-47272 and fix it if it is affected.

What it is: CVE-2026-47272 is a high-severity authentication bypass vulnerability in mcdope pam_usb, published on 27 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-47272 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-2026-47272/ (Markdown: https://insights.sbomify.com/CVE-2026-47272/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-47272
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-47272
- OSV: https://osv.dev/vulnerability/CVE-2026-47272

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-47272/
Summaries are generated and may contain mistakes; the official description above is the record.