CVE-2026-24515 is a vulnerability identified in the libexpat XML parsing library, specifically in versions prior to 2.7.4. The issue arises in the XML_ExternalEntityParserCreate function, which fails to properly copy user data associated with unknown encoding handlers. This improper handling leads to a NULL pointer dereference (CWE-476), which can cause the application using libexpat to crash when processing certain crafted XML inputs. The vulnerability does not allow for code execution or data leakage but results in a denial of service (DoS) condition by terminating the affected process unexpectedly. The CVSS v3.1 score is 2.9, reflecting low severity due to the requirement for local access, high attack complexity, and no privileges or user interaction needed. The flaw is primarily an availability concern, with no impact on confidentiality or integrity. No public exploits have been reported, and no patches were linked in the provided data, but the issue is fixed in libexpat version 2.7.4. The vulnerability affects software that embeds libexpat for XML parsing, which is common in many open-source and commercial applications. Attackers would need to supply malicious XML data to trigger the crash, which is feasible in environments where XML input is processed locally or from trusted sources. The flaw highlights the importance of robust error handling in XML parsers to prevent service disruptions.

For European organizations, the primary impact of CVE-2026-24515 is potential denial of service due to application crashes when processing malformed XML data. This could disrupt services that rely on XML parsing, such as web servers, middleware, or enterprise applications embedding libexpat. Although the vulnerability does not compromise data confidentiality or integrity, availability interruptions can affect business continuity, especially in critical infrastructure or service providers. Organizations with legacy systems or embedded devices using outdated libexpat versions are more vulnerable. The low exploitability and lack of known exploits reduce immediate risk, but targeted attacks or accidental crashes could still cause operational issues. The impact is more pronounced in sectors with heavy XML usage, including finance, telecommunications, and government services. Proper patching and input validation can prevent exploitation and maintain service reliability.

To mitigate CVE-2026-24515, organizations should: 1) Upgrade libexpat to version 2.7.4 or later where the vulnerability is resolved. 2) Audit software dependencies to identify and update applications embedding vulnerable libexpat versions. 3) Implement strict input validation and sanitization for XML data, especially from untrusted or external sources, to reduce the risk of triggering the NULL pointer dereference. 4) Employ runtime monitoring and crash detection mechanisms to quickly identify and respond to application failures related to XML parsing. 5) For embedded or legacy systems where upgrading is challenging, consider isolating XML processing components or applying compensating controls such as sandboxing. 6) Maintain an inventory of systems using libexpat to prioritize patching efforts. 7) Engage with vendors for timely updates if libexpat is bundled within third-party products.