CVE-2024-23807 is a use-after-free vulnerability identified in the Apache Xerces C++ XML parser, specifically affecting versions from 3.0.0 up to but not including 3.2.5. The flaw is triggered during the processing of external Document Type Definitions (DTDs), a feature used to define the structure and legal elements of XML documents. The vulnerability arises when the parser incorrectly manages memory, freeing an object prematurely and subsequently accessing it, which can lead to memory corruption. This can be exploited remotely by an attacker who crafts malicious XML content containing external DTD references, potentially leading to arbitrary code execution or denial of service (application crash). Notably, the vulnerability does not require any authentication or user interaction, increasing its risk profile. The issue was previously disclosed as CVE-2018-1311 but was mistakenly believed to be fixed in versions 3.2.3 or 3.2.4; the actual fix was implemented in version 3.2.5. Mitigation options include upgrading to version 3.2.5 or disabling DTD processing entirely, which can be done through parser configuration settings (e.g., disabling DTD via DOM parser features or setting the XERCES_DISABLE_DTD environment variable for SAX parsers). The CVSS v3.1 base score of 8.1 reflects the vulnerability's high impact on confidentiality, integrity, and availability, with a network attack vector, high attack complexity, and no privileges or user interaction required.

For European organizations, this vulnerability poses a significant risk especially for those relying on Apache Xerces C++ for XML parsing in critical applications such as financial services, government systems, telecommunications, and industrial control systems. Exploitation could lead to unauthorized code execution, allowing attackers to compromise sensitive data, disrupt services, or pivot within networks. The ability to cause denial of service could affect availability of essential services, impacting business continuity and operational reliability. Given the widespread use of XML parsing in software libraries and embedded systems, the scope of affected systems can be broad. Organizations that process untrusted XML input or expose XML parsing services to external networks are particularly vulnerable. The lack of required authentication or user interaction means attackers can exploit this remotely with relative ease, increasing the threat level. Failure to address this vulnerability could lead to data breaches, service outages, and reputational damage.

European organizations should immediately assess their use of Apache Xerces C++ and identify any systems running affected versions prior to 3.2.5. The primary mitigation is to upgrade all affected instances to version 3.2.5 or later, which contains the official fix. If upgrading is not immediately feasible, organizations should disable DTD processing to prevent exploitation; this can be done by configuring the DOM parser to disable DTD features or setting the XERCES_DISABLE_DTD environment variable for SAX parsers. Additionally, organizations should implement network-level protections such as input validation and XML schema validation to reject malicious XML documents before parsing. Monitoring and logging XML parsing errors and unusual application behavior can help detect exploitation attempts. Security teams should also review and update incident response plans to address potential exploitation scenarios. Finally, vendors embedding Apache Xerces C++ in their products should be engaged to ensure timely patching and mitigation.