CVE-2026-48981

CVE-2026-48981 is a medium-severity vulnerability with a CVSS 3.x base score of 6.7. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-611.

Key facts

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.

Frequently asked questions

What is 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.
How severe is CVE-2026-48981?
CVE-2026-48981 has a CVSS 3.x base score of 6.7, rated medium severity. It is exploitable over local access with high attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity low, and availability low.
Is CVE-2026-48981 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (2nd percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-48981?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-48981 have an EU (EUVD) identifier?
Yes. CVE-2026-48981 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-37934.
When was CVE-2026-48981 published?
CVE-2026-48981 was published on 2026-06-18 and last updated on 2026-06-22.

References

Other CWE-611 (Improper Restriction of XML External Entity Reference (XXE)) vulnerabilities

Browse all CWE-611 (Improper Restriction of XML External Entity Reference (XXE)) vulnerabilities →