What’s Vulnerable › Vulnerabilities

CVE-2026-48981: pam_usb: xmlReadFile flags=0 permits XXE network entity fetching in conf.c

• Severity: medium (CVSS 6.7 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-06-18 · updated 2026-10-26
• Weakness: CWE-611

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.

Affected products

• mcdope pam_usb: before 0.9.2

References

• https://github.com/mcdope/pam_usb/releases/tag/0.9.2
• https://github.com/mcdope/pam_usb/security/advisories/GHSA-96vv-r4wc-28c2

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