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CVE-2026-48064

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

Published: May 27, 2026Updated: May 27, 2026 Sources: CVE List NVD
NVD MITRE
8.1CVSS
HIGH

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.

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

CVSS Vector Breakdown

AV:NAC:HPR:NUI:NS:UC:HI:HA:H
Exploitability
AV:NAttack Vector
Network
AC:HAttack Complexity
High
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:HAvailability
High

Weaknesses

CWE-863

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

2 techniques
Initial Access
View detailed technique mapping

References

https://github.com/mcdope/pam_usb/issues/348
github.com
https://github.com/mcdope/pam_usb/security/advisories/GHSA-w38v-cw9r-x9p6
github.com

Timeline

Published
May 27, 2026
Last Updated
May 27, 2026

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