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

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Summary

CVECVE-2026-48064
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-27 20:16:40 UTC
Updated2026-05-28 13:57:25 UTC
Descriptionpam_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.

Risk And Classification

Primary CVSS: v3.1 8.1 HIGH from [email protected]

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Problem Types: CWE-863 | CWE-863 CWE-863: Incorrect Authorization

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary8.1HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED8.1HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Mcdope Pam Usb affected < 0.9.1 Not specified

References

ReferenceSourceLinkTags
github.com/mcdope/pam_usb/issues/348 [email protected] github.com
github.com/mcdope/pam_usb/security/advisories/GHSA-w38v-cw9r-x9p6 [email protected] github.com
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