CVE-2024-34459 is a buffer over-read vulnerability identified in the xmllint utility, part of the widely used libxml2 XML parsing library. The issue specifically occurs when xmllint is invoked with the --htmlout option to format error messages. The vulnerability resides in the xmlHTMLPrintFileContext function within xmllint.c, where improper handling of buffer boundaries during error message formatting leads to reading beyond the allocated buffer. This flaw is classified under CWE-122 (Heap-based Buffer Over-read). The vulnerability affects libxml2 versions prior to 2.11.8 and 2.12.x versions before 2.12.7. Exploitation requires no privileges or user interaction and can be triggered remotely by supplying crafted XML input that causes xmllint to generate error messages processed with the --htmlout flag. The buffer over-read can lead to disclosure of sensitive memory contents, impacting confidentiality. Although no exploits have been reported in the wild, the vulnerability's characteristics and the widespread deployment of libxml2 in many Linux distributions, software applications, and embedded systems make it a significant concern. The CVSS v3.1 base score is 7.5, reflecting high severity due to network attack vector, low attack complexity, no privileges required, no user interaction, and a high impact on confidentiality without affecting integrity or availability. The vulnerability underscores the importance of updating to patched versions 2.11.8 or 2.12.7 and beyond to mitigate potential data leakage risks.

For European organizations, the primary impact of CVE-2024-34459 is the potential unauthorized disclosure of sensitive information due to buffer over-read in xmllint error message formatting. Organizations that use libxml2 and xmllint in automated XML processing pipelines, web services, or security tools may inadvertently expose memory contents that could include confidential data or cryptographic material. This can lead to breaches of data protection regulations such as GDPR, resulting in legal and financial consequences. The vulnerability does not affect integrity or availability directly but compromises confidentiality, which is critical for sectors handling sensitive personal, financial, or governmental data. The ease of remote exploitation without authentication increases the risk, especially for internet-facing systems or those processing untrusted XML inputs. European critical infrastructure, financial institutions, and technology companies relying on open-source XML libraries are particularly vulnerable. The absence of known exploits in the wild provides a window for proactive mitigation, but the widespread use of libxml2 means the attack surface is broad.

1. Immediately upgrade libxml2 to version 2.11.8 or 2.12.7 or later, where the vulnerability is patched. 2. Audit all systems and applications that utilize xmllint or libxml2 for XML processing, especially those using the --htmlout option, to identify and remediate vulnerable instances. 3. Restrict or sanitize XML inputs from untrusted sources to reduce the risk of triggering the vulnerability. 4. Implement network-level controls to limit exposure of services that process XML data with xmllint, including firewall rules and segmentation. 5. Monitor logs and network traffic for unusual XML parsing errors or attempts to exploit xmllint error formatting. 6. Consider deploying runtime application self-protection (RASP) or memory safety tools to detect and prevent buffer over-read attempts. 7. Educate development and operations teams about the vulnerability and the importance of timely patching and secure XML handling practices.