Executive brief
libexpat is a widely used software library for processing XML data in various applications and operating systems. A flaw in how it handles data buffers could allow an attacker to cause an integer overflow, potentially leading to unauthorized data access or system instability. This issue is particularly relevant for software that processes untrusted XML input using specific internal functions.
Technical details
An integer overflow vulnerability exists in libexpat versions prior to 2.8.2 within the XML_ParseBuffer function. The root cause is a missing safety check for buffer indices that was already implemented in the related XML_Parse function. An attacker could exploit this by providing specially crafted XML input to an application using the vulnerable function, potentially leading to memory corruption, information disclosure, or a denial-of-service condition. The attack vector is local with high complexity, as it requires the target application to utilize the specific XML_ParseBuffer API in a way that triggers the overflow. The issue has been addressed in version 2.8.2.
Affected products
- libexpat project libexpat before 2.8.2
Timeline
- 2026-05-31: patched: Fix merged into libexpat master branch via pull request 1255
- 2026-06-21: disclosed: CVE-2026-56406 published