XXE in Mcdope Pam Usb

CVE-2026-48981

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.

Vulnerability class: XXE (XML External Entity)

Published · last modified .

CVSS v3 metric

CVSS v3 base score 6.7 (Medium). Vector: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:L/A:L.

EPSS exploit prediction

EPSS: 0.002 (4.0th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 4th percentile — 4.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-48981: held from 0.002 to 0.002.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-48981?
CVE-2026-48981 is a medium-severity vulnerability in Mcdope Pam Usb, classified under Improper Restriction of XML External Entity Reference (XXE). CVSS score: 6.7/10. Published 2026-06-18.
How severe is CVE-2026-48981?
Medium severity. CVSS v3 base score is 6.7 out of 10.