CVE-2026-48981
pam_usb: xmlReadFile flags=0 permits XXE network entity fetching in conf.c
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.
INFO
Published Date :
June 18, 2026, 8:16 p.m.
Last Modified :
Oct. 26, 2026, 11:10 a.m.
Remotely Exploit :
No
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update pam_usb to version 0.9.2 or later.
- Review configuration files for malicious XML entities.
- Restrict write access to pam_usb.conf.
- Monitor processes running in setuid contexts.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-48981.
| URL | Resource |
|---|---|
| https://github.com/mcdope/pam_usb/releases/tag/0.9.2 | |
| https://github.com/mcdope/pam_usb/security/advisories/GHSA-96vv-r4wc-28c2 |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-48981 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-48981
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-48981 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-48981 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Translated by [email protected]
Oct. 26, 2026
Action Type Old Value New Value Added Translation Title: pam_usb de mcdope, Description: pam_usb proporciona autenticación de hardware para Linux utilizando medios extraíbles ordinarios. En versiones anteriores a la 0.9.2, pam_usb llama a xmlReadFile() con flags=0 al cargar el archivo de configuración, permitiendo a libxml2 procesar referencias a entidades externas (XXE), lo que podría permitir realizar conexiones de red salientes o lecturas de archivos locales en el momento del análisis XML desde el contexto del proceso de autenticación. La vulnerabilidad requiere que el archivo de configuración contenga referencias a entidades XML manipuladas. Dado que pam_usb.conf es propiedad de root, la explotación directa requiere acceso de escritura previo a la configuración, pero el impacto en la defensa en profundidad es significativo dado que pam_usb.so se ejecuta en contextos setuid (sudo, su). Este problema ha sido solucionado en la versión 0.9.2. -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 22, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-48981', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-06-22T15:19:25.463710Z'} -
New CVE Received by [email protected]
Jun. 18, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'mcdope', 'product': 'pam_usb', 'versions': [{'status': 'affected', 'version': '< 0.9.2'}]}] Added 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. Added CVSS V3.1 AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:L/A:L Added CWE CWE-611 Added Reference https://github.com/mcdope/pam_usb/releases/tag/0.9.2 Added Reference https://github.com/mcdope/pam_usb/security/advisories/GHSA-96vv-r4wc-28c2