CVE-2026-24515 is a vulnerability identified in the libexpat XML parsing library, specifically affecting versions prior to 2.7.4. The issue arises in the function XML_ExternalEntityParserCreate, which is responsible for creating parsers for external XML entities. The vulnerability is due to the function's failure to correctly copy user data associated with unknown encoding handlers, leading to a NULL pointer dereference (CWE-476). When an application using the vulnerable libexpat version processes XML input that triggers this condition, it may dereference a NULL pointer, causing the application to crash and resulting in a denial of service (DoS). The CVSS v3.1 base score is 2.9, reflecting low severity, with attack vector local (AV:L), high attack complexity (AC:H), no privileges required (PR:N), no user interaction (UI:N), unchanged scope (S:U), and impact limited to availability (A:L). This means exploitation requires local access and is difficult to perform, but no authentication or user interaction is needed. There are no known public exploits or active exploitation reported. The vulnerability affects software that relies on libexpat for XML parsing, which is widely used in various applications and systems. The patch for this vulnerability is included starting from libexpat version 2.7.4, which corrects the handling of unknown encoding handler user data to prevent the NULL pointer dereference. Organizations using older versions should upgrade promptly to avoid potential service disruptions.

The primary impact of CVE-2026-24515 is a denial of service caused by application crashes due to NULL pointer dereference when parsing crafted XML input. For European organizations, this could disrupt services that rely on libexpat for XML processing, including web servers, middleware, and embedded systems. Although the attack requires local access and has high complexity, insider threats or compromised internal systems could exploit this vulnerability to cause outages. The impact on confidentiality and integrity is negligible, but availability degradation could affect critical business operations, especially in sectors like finance, telecommunications, and government services where XML processing is common. The lack of known exploits and the low CVSS score suggest limited immediate risk, but unpatched systems remain vulnerable to potential targeted attacks or accidental crashes. Organizations with legacy systems or custom software embedding older libexpat versions are at higher risk. Ensuring availability and reliability of XML-dependent services is crucial to avoid operational disruptions.

To mitigate CVE-2026-24515, European organizations should: 1) Upgrade all libexpat instances to version 2.7.4 or later, where the vulnerability is fixed. 2) Conduct an inventory of software and systems using libexpat, including embedded devices and third-party applications, to identify vulnerable versions. 3) Implement strict input validation and sanitization for XML data, especially when handling external entities or unknown encodings. 4) Employ application-level monitoring to detect crashes or abnormal terminations related to XML parsing. 5) Restrict local access to systems running vulnerable libexpat versions to trusted personnel only, reducing the risk of local exploitation. 6) Review and harden XML parser configurations to disable or limit external entity processing where not required. 7) Collaborate with software vendors to ensure timely patching of embedded libexpat components. These targeted actions go beyond generic advice by focusing on the specific nature of the vulnerability and its exploitation requirements.