CVE-2024-56171 is a use-after-free vulnerability classified under CWE-416 found in the libxml2 library, specifically in the xmlschemas.c source file within the functions xmlSchemaIDCFillNodeTables and xmlSchemaBubbleIDCNodeTables. Libxml2 is a widely used open-source XML parsing library employed in many software products and systems for XML document processing and validation. The vulnerability arises when libxml2 processes XML schemas containing certain identity constraints, which are rules that enforce uniqueness and referential integrity within XML documents. An attacker can craft a malicious XML document or XML schema that triggers the use-after-free condition during schema validation. This memory corruption flaw can lead to arbitrary code execution or data leakage by corrupting internal data structures, thereby compromising confidentiality and integrity. Exploitation requires local access (AV:L) and high attack complexity (AC:H), with no privileges or user interaction needed. The vulnerability affects libxml2 versions prior to 2.12.10 and 2.13.x versions before 2.13.6. Although no exploits are currently known in the wild, the high CVSS score of 7.8 reflects the potential for serious impact if weaponized. The scope is considered changed (S:C) because the vulnerability can affect other components relying on libxml2 for XML schema validation. The vulnerability is critical for environments that perform automated XML schema validation, such as web services, middleware, and document processing systems.

For European organizations, the impact of CVE-2024-56171 can be significant, especially in sectors relying heavily on XML processing such as finance, telecommunications, government, and critical infrastructure. Exploitation could allow attackers to bypass security controls, access sensitive data, or execute arbitrary code within affected applications, leading to data breaches or service disruptions. Since libxml2 is embedded in many open-source and commercial products, the vulnerability could propagate through supply chains, affecting a broad range of systems. The requirement for local access limits remote exploitation but insider threats or compromised internal systems could leverage this vulnerability. The confidentiality and integrity of data processed via XML schemas are at high risk, which is critical for compliance with GDPR and other European data protection regulations. The absence of known exploits provides a window for proactive mitigation, but organizations must act swiftly to prevent potential future attacks.

1. Immediately upgrade libxml2 to version 2.12.10 or 2.13.6 or later to ensure the vulnerability is patched. 2. Audit all software and systems that use libxml2 for XML schema validation, including third-party applications and middleware, to identify vulnerable versions. 3. Implement strict input validation and filtering on XML documents and schemas received from untrusted sources to reduce the risk of crafted malicious inputs. 4. Restrict local access to systems performing XML schema validation to trusted users and processes only, minimizing the attack surface. 5. Monitor logs and system behavior for anomalies during XML processing that could indicate exploitation attempts. 6. Engage with vendors and open-source communities to track updates and patches related to libxml2 and related dependencies. 7. Consider deploying runtime memory protection mechanisms such as Address Space Layout Randomization (ASLR) and Control Flow Integrity (CFI) to mitigate exploitation impact. 8. Conduct regular security assessments and penetration testing focusing on XML processing components to detect potential weaknesses.