CVE-2026-11979: xmlsoft libxml2 Stack-based Buffer Overflow

Vulnerability summary

CVE-2026-11979 is a high (CVSS 7.8) Stack-based Buffer Overflow vulnerability in xmlsoft libxml2. EPSS estimates a 0.15% chance of exploitation in the next 30 days, higher than 3.6% of scored vulnerabilities.

Timeline

1. 29-06-2026
   PublishedVulnerability first disclosed.
2. 29-06-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-121Stack-based Buffer OverflowA stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).