pam_usb: xmlReadFile flags=0 permits XXE network entity fetching in conf.c

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Summary

CVECVE-2026-48981
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-18 20:16:14 UTC
Updated2026-06-22 17:56:35 UTC
Descriptionpam_usb provides hardware authentication for Linux using ordinary removable media. In versions prior to 0.9.2, pam_usb calls xmlReadFile() with flags=0 when loading the configuration file, allowing libxml2 to process external entity references (XXE), potentially making outbound network connections or local file reads at XML parse time from the context of the authenticating process. The vulnerability requires the configuration file to contain crafted XML entity references. Since pam_usb.conf is root-owned, direct exploitation requires prior write access to the config, but the defence-in-depth impact is significant given that pam_usb.so runs in setuid contexts (sudo, su). This issue has been fixed in version 0.9.2.

Risk And Classification

Primary CVSS: v3.1 6.7 MEDIUM from [email protected]

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

Problem Types: CWE-611 | CWE-611 CWE-611: Improper Restriction of XML External Entity Reference

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6.7MEDIUMCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:L/A:L
3.1CNADECLARED6.7MEDIUMCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:L/A:L

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
High
Privileges Required
High
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
Low
Availability
Low

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Mcdope Pam Usb affected < 0.9.2 Not specified

References

ReferenceSourceLinkTags
github.com/mcdope/pam_usb/releases/tag/0.9.2 [email protected] github.com
github.com/mcdope/pam_usb/security/advisories/GHSA-96vv-r4wc-28c2 [email protected] github.com
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