pam_usb: pusb_has_virtual_input_device() silently discards EACCES, disabling remote desktop detection under non-root execution

published 2026-05-27 5mo ago modified 2026-10-26 16d ago also EUVD-2026-32647

cvss: 4.4; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.1%; EPSS 0.1% chance of exploitation in 30 days, percentile 2%
public exploits: 0; none known

pam_usb provides hardware authentication for Linux using ordinary removable media. Prior to 0.9.1, src/evdev.c silently ignores EACCES errors when opening /dev/input/event* nodes, causing pusb_has_virtual_input_device() to return 0 (no virtual devices found) even when every open() call failed due to insufficient permissions. The caller in src/local.c cannot distinguish a clean absence of virtual devices from a permission-denied scan, and acts on the false negative by continuing authentication without denying. This vulnerability is fixed in 0.9.1.

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CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 5mo ago (2026-05-28)

Exploit prediction

0.13% chance of exploitation in the next 30 days, higher than 2% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by	version	score	vector
CNA	3.1	4.4	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

Affected products

mcdope pam_usb

Classification

Weakness

CWE-390 Detection of Error Condition Without Action
CWE-693 Protection Mechanism Failure

References

Sources

CVE List CVE-2026-48792
NVD CVE-2026-48792

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