CVE-2026-48064

HIGH

pam_usb: PAM_RHOST check skipped when deny_remote=false allows XDMCP authentication bypass

Title source: cna
STIX 2.1

Description

pam_usb provides hardware authentication for Linux using ordinary removable media. Prior to 0.9.1, when a PAM service is configured with deny_remote=false in pam_usb (commonly done for display managers such as gdm-password or lightdm to bypass process/TTY heuristics for local sessions), the PAM_RHOST check in pusb_do_auth() is also skipped. PAM_RHOST is set by remote daemons (sshd, XDMCP servers) to identify the remote client address. Because the check is gated inside if (opts.deny_remote), a genuine remote XDMCP connection reaches the USB device authentication step instead of being rejected. This vulnerability is fixed in 0.9.1.

References (2)

Core 2
Core References
X_Refsource_Misc x_refsource_misc
https://github.com/mcdope/pam_usb/issues/348

Scores

CVSS v3 8.1
EPSS 0.0034
EPSS Percentile 25.9%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

CISA SSVC

Vulnrichment
Exploitation poc
Automatable no
Technical Impact total

Details

CWE
CWE-863
Status published
Products (1)
mcdope/pam_usb < 0.9.1
Published May 27, 2026
Tracked Since May 28, 2026