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CVE-2026-47272

pam_usb: OTP pad authentication bypass via missing system pad check and uninitialized RNG buffer

Published: May 27, 2026Updated: May 27, 2026 Sources: CVE List NVD
NVD MITRE
7.1CVSS
HIGH

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.

EPSS Score
N/A
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
No Fix Available

CVSS Vector Breakdown

AV:LAC:LPR:LUI:NS:UC:HI:HA:N
Exploitability
AV:LAttack Vector
Local
AC:LAttack Complexity
Low
PR:LPrivileges Required
Low
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:NAvailability
None

Weaknesses

CWE-287CWE-908

Affected Products

pam_usb
mcdope

Attack Graph

Products CVE Techniques Tactics

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Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.

MITRE ATT&CK

3 techniques
Collection
Initial Access
View detailed technique mapping

References

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

Timeline

Published
May 27, 2026
Last Updated
May 27, 2026

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