CVE-2026-48981 Details
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.
A vulnerability in pam_usb versions prior to 0.9.2 allows for XML External Entity (XXE) attacks. The issue arises because pam_usb calls xmlReadFile() with flags=0 when loading the configuration file, enabling libxml2 to process external entity references. This could lead to outbound network connections or local file reads during XML parsing, from the context of the authenticating process. Exploitation requires the configuration file to contain crafted XML entity references. While pam_usb.conf is root-owned, direct exploitation would need prior write access to the config. However, the issue is particularly concerning because pam_usb.so operates in setuid contexts, such as with sudo or su.
Users are advised to upgrade to pam_usb version 0.9.2, which disables XXE processing by passing appropriate flags to xmlReadFile().
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Jun 18, 2026CISA-ADP
Assessed Jun 22, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/mcdope/pam_usb/releases/tag/0.9.2 | [email protected] | Release NotesVendor |
| https://github.com/mcdope/pam_usb/security/advisories/GHSA-96vv-r4wc-28c2 | [email protected] | AdvisoryRemedyVendor |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-611 | Improper Restriction of XML External Entity Reference | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| mcdope pam_usb | <= 0.9.1 (semver) |
CPE
Remediation
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Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 22, 2026 | CVE Modified | CISA-ADP |
| Jun 18, 2026 | New CVE Received | [email protected] |