Vulnerability · Published May 27, 2026 · Assigned by GitHub_M
CVE-2026-47272pam_usb: OTP pad authentication bypass via missing system pad check and uninitialized RNG buffer
High 7.1
In plain English
A high-severity improper authentication in pam_usb from mcdope. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 2% of all known vulnerabilities).
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.
Affected products (as reported)
Weakness: CWE-287, CWE-908 · Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
References
- https://github.com/mcdope/pam_usb/security/advisories/GHSA-vx6f-rrqr-j87c x_refsource_CONFIRM