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

Description (CNA)

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 (CNA)

Vendor / product	Versions
mcdope / pam_usb	affected < 0.9.0

CWE

CWE-287, CWE-908

References

https://github.com/mcdope/pam_usb/security/advisories/GHSA-vx6f-rrqr-j87c

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.