libexpat XML parsing library Vulnerability >>>

The CERT Coordination Center (CERT/CC) has issued a vulnerability note warning of a stack overflow flaw in the libexpat XML parsing library, tracked as CVE-2024-8176. This vulnerability, carrying a CVSS score of 7.5, could allow attackers to crash applications or potentially trigger memory corruption—depending on how the library is deployed in affected environments.
libexpat is an open-source, stream-oriented XML parser written in C. It’s widely used in a variety of software ecosystems, especially in systems that need to process large XML files efficiently.
libexpat is used in a variety of different software, and by various companies. Because of its extensive use across platforms—from embedded systems to large-scale enterprise software—vulnerabilities in libexpat can have wide-reaching impact.


The root of the vulnerability lies in the way libexpat handles recursive entity expansion. When specially crafted XML files are parsed, an attacker can nest entity references deeply enough to cause unbounded recursion, leading to a stack overflow.
“A stack overflow vulnerability exists… When parsing an XML document with deeply nested entity references, libexpat can be forced to recurse indefinitely,” CERT/CC explains.
This unbounded recursion results in denial-of-service (DoS) conditions and, under specific conditions, may lead to exploitable memory corruption, opening the door to more severe attacks.
Any software that parses XML using unpatched versions of libexpat is vulnerable. Attackers don’t need elevated privileges—they only need to feed a malicious XML file to the system using libexpat.
“An attacker… could provide a XML document to the program and cause a DoS attack or memory corruption attack,” CERT/CC warns.
The widespread integration of libexpat into numerous open-source and commercial projects makes supply chain risks a major concern.
A fix for the vulnerability is available in libexpat version 2.7.0. Developers and maintainers are strongly urged to update immediately and verify protection using the proof-of-concept (PoC) payloads provided in the official GitHub issue.
The flaw was responsibly disclosed by Jann Horn of Google’s Project Zero.