CVE-2026-48981: CWE-611: Improper Restriction of XML External Entity Reference in mcdope pam_usb
pam_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.
AI Analysis
Technical Summary
The vulnerability in pam_usb before version 0.9.2 arises from the use of xmlReadFile() with flags=0, which permits libxml2 to process external entity references (XXE) in the configuration file. This can lead to unintended network connections or local file reads during XML parsing by the authenticating process. Since the configuration file is root-owned, exploitation requires prior write access to this file. Given that pam_usb.so operates in setuid contexts, the impact on defense-in-depth is significant. The vulnerability is addressed in pam_usb version 0.9.2.
Potential Impact
Successful exploitation can lead to disclosure of local files or outbound network connections from the context of the authenticating process, which runs with elevated privileges due to setuid. This can compromise confidentiality (high impact), cause limited integrity loss, and availability impact. However, exploitation requires prior write access to the root-owned configuration file, limiting direct attack vectors.
Mitigation Recommendations
Upgrade pam_usb to version 0.9.2 or later where this vulnerability is fixed. Since the vulnerability requires a crafted configuration file, ensure strict access controls on pam_usb.conf to prevent unauthorized modifications. Patch status is confirmed fixed in version 0.9.2.
CVE-2026-48981: CWE-611: Improper Restriction of XML External Entity Reference in mcdope pam_usb
Description
pam_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.
CVSS v3.1
Score 6.7medium
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in pam_usb before version 0.9.2 arises from the use of xmlReadFile() with flags=0, which permits libxml2 to process external entity references (XXE) in the configuration file. This can lead to unintended network connections or local file reads during XML parsing by the authenticating process. Since the configuration file is root-owned, exploitation requires prior write access to this file. Given that pam_usb.so operates in setuid contexts, the impact on defense-in-depth is significant. The vulnerability is addressed in pam_usb version 0.9.2.
Potential Impact
Successful exploitation can lead to disclosure of local files or outbound network connections from the context of the authenticating process, which runs with elevated privileges due to setuid. This can compromise confidentiality (high impact), cause limited integrity loss, and availability impact. However, exploitation requires prior write access to the root-owned configuration file, limiting direct attack vectors.
Mitigation Recommendations
Upgrade pam_usb to version 0.9.2 or later where this vulnerability is fixed. Since the vulnerability requires a crafted configuration file, ensure strict access controls on pam_usb.conf to prevent unauthorized modifications. Patch status is confirmed fixed in version 0.9.2.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-05-26T23:26:07.974Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a344c3bf198dc38c1709d7c
Added to database: 06/18/2026, 19:51:23 UTC
Last enriched: 06/25/2026, 21:17:11 UTC
Last updated: 08/01/2026, 07:18:01 UTC
Views: 91
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