# CVE-2026-47272: pam_usb authentication bypass in pusb_pad_compare

Source: https://junglewise.ai/threats/cve-2026-47272-pam-usb-authentication-bypass-in-pusb-pad-compare  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-27. Updated: 2026-05-27  
License: CC BY 4.0 with a link back

CVE-2026-47272 · Severity: high · CVSS 7.1 · Published 2026-05-27

pam_usb is a tool that allows users to log into Linux systems using a physical USB drive as a security key. A flaw in how the software checks for these security keys allows a local user to bypass the hardware requirement entirely by deleting a specific file in their home directory. This effectively disables the multi-factor authentication, allowing unauthorized access to the system without the required physical USB device.

Technologies: [Mcdope Pam Usb](https://junglewise.ai/threats/technologies/pam-usb). Vendors: [Mcdope](https://junglewise.ai/threats/vendors/mcdope).

## Quick answers

**Is CVE-2026-47272 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-47272 being exploited in the wild.

**How severe is CVE-2026-47272?** High severity, with a CVSS score of 7.1, published 27 May 2026.

**Which products and versions are affected?** Mcdope Pam Usb < 0.9.0.

**Is there a fix for CVE-2026-47272?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-47272 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-47272?** Check whether you run Mcdope Pam Usb at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability exists in the pusb_pad_compare() function within src/pad.c of pam_usb. The function fails to enforce that the system-side pad (stored on the USB device) is present and readable, only verifying the user-side pad (~/.pamusb/device.pad). If the user-side pad is missing or unreadable, the function returns a failure that is treated as non-fatal in certain code paths, allowing authentication to proceed without verifying the physical hardware. Additionally, a secondary issue involves the use of uninitialized stack memory when generating random pads if /dev/random fails to provide sufficient bytes. These issues are addressed in version 0.9.0 by implementing symmetrical pad verification and switching to getrandom(2).

## Affected products

- mcdope pam_usb < 0.9.0

## Timeline

- 2026-05-20: advisory: GitHub Security Advisory published
- 2026-05-27: disclosed: CVE published to NVD

## References

- [https://github.com/mcdope/pam_usb/security/advisories/GHSA-vx6f-rrqr-j87c](https://github.com/mcdope/pam_usb/security/advisories/GHSA-vx6f-rrqr-j87c)

## Related threats

- [pam_usb heap out-of-bounds read in display server handling](https://junglewise.ai/threats/cve-2026-64667-pam-usb-provides-hardware-authentication-for-linux-using)
- [pam_usb XRDP session bypass via environment variable](https://junglewise.ai/threats/cve-2026-64666-pam-usb-provides-hardware-authentication-for-linux-using)
- [mcdope pam_usb symlink race condition in pad directory creation](https://junglewise.ai/threats/cve-2026-48983-mcdope-pam-usb-symlink-race-condition-in-pad-directory-creation)
- [mcdope pam_usb race condition in one-time pad update](https://junglewise.ai/threats/cve-2026-48982-mcdope-pam-usb-race-condition-in-one-time-pad-update)
- [mcdope pam_usb XXE in configuration file parsing](https://junglewise.ai/threats/cve-2026-48981-mcdope-pam-usb-xxe-in-configuration-file-parsing)