Executive brief
libxml2 is a widely-used XML parsing library embedded in many applications and operating systems. An integer overflow vulnerability in the URI escaping function can cause memory corruption when processing specially crafted XML URIs, potentially leading to application crashes or arbitrary code execution.
Technical details
The vulnerability is an integer overflow in the xmlURIEscapeStr function in uri.c. When xmlStrlen() returns 0 for strings longer than INT_MAX, the code adds 20 to the length without validation, causing len to wrap to a small value. This leads to undersized buffer allocation and subsequent heap overflow when writing escaped URI characters. The vulnerability is triggered when processing a specially crafted URI string; network reachability depends on the calling application's exposure to untrusted XML input. The fix in libxml2 2.15.4 adds a length check to return NULL when xmlStrlen returns 0, preventing the overflow.
Affected products
- GNOME libxml2 before 2.15.4
Timeline
- 2026-09-05: disclosed
- 2.15.4: patched