Description

CERT Polska has received a report about vulnerability in xmlsoft libxml2 software and participated in coordination of its disclosure.

The vulnerability CVE-2026-11979: libxml2 is vulnerable to multiple stack-based buffer overflows in the xmlcatalog utility when running in --shell mode. The usershell() function processes user input using fixed-size stack buffers without proper bounds checking. By supplying an overly long input line, an attacker can overflow internal buffers (command, arg, and argv) during input parsing. This results in memory corruption within the stack frame. Successful exploitation may cause a crash or potentially allow arbitrary code execution in the context of the xmlcatalog process.

This issue has been fixed in the commit c2e233fc.

NOTE: The maintainers of this project did not agree that this issue is a vulnerability and considered it a bug.

Credits

We thank Michal Majchrowicz and Marcin Wyczechowski (AFINE) for the responsible vulnerability report.