CVE-2023-52426 is a vulnerability identified in libexpat, a widely used XML parsing library, affecting versions up to 2.5.0. The issue arises when libexpat is compiled without defining XML_DTD, which enables recursive XML Entity Expansion (XEE). This recursive expansion can lead to excessive resource consumption, effectively causing a denial of service (DoS) condition. The vulnerability is classified under CWE-776, which relates to improper restriction of recursive entity references in XML. The attack vector is local (AV:L), requiring the attacker to have local privileges on the system. The attack complexity is low (AC:L), and no user interaction is needed (UI:N). The scope is unchanged (S:U), meaning the impact is confined to the vulnerable component. The vulnerability impacts availability (A:H) but does not affect confidentiality or integrity. No known exploits have been reported in the wild, and no patches have been officially released at the time of publication. The absence of XML_DTD definition at compile time is a critical factor, suggesting that systems using custom or minimal builds of libexpat are at higher risk. This vulnerability can be exploited by crafting malicious XML inputs that trigger recursive entity expansion, exhausting CPU and memory resources during parsing. Given libexpat's extensive use in various software, including embedded systems, applications, and services that process XML locally, this vulnerability can disrupt normal operations if exploited.

For European organizations, the primary impact of CVE-2023-52426 is the potential for denial of service attacks on systems that utilize libexpat for XML parsing, particularly those compiled without XML_DTD support. This can lead to service outages, degraded performance, and operational disruptions in critical infrastructure, software applications, and embedded devices. Industries relying heavily on XML processing, such as telecommunications, manufacturing, automotive, and financial services, may face increased risk. The requirement for local access limits remote exploitation, but insider threats or compromised local accounts could leverage this vulnerability to disrupt services. The lack of confidentiality or integrity impact reduces the risk of data breaches, but availability issues can still cause significant business interruptions and financial losses. Additionally, embedded systems and IoT devices using vulnerable libexpat versions may be particularly susceptible, potentially affecting supply chains and industrial control systems prevalent in Europe.

To mitigate CVE-2023-52426, organizations should first identify all instances of libexpat in their environments, focusing on versions up to 2.5.0 and verifying if XML_DTD was undefined at compile time. Recompiling libexpat with XML_DTD defined is a direct mitigation to prevent recursive entity expansion. Until official patches are released, consider applying custom patches or configuration changes that disable or limit entity expansion in XML parsers. Implement strict access controls to limit local user privileges and reduce the risk of exploitation by unauthorized users. Monitor XML processing logs for unusual or recursive entity patterns that could indicate exploitation attempts. For embedded systems, coordinate with vendors to obtain updated firmware or software versions that address this vulnerability. Additionally, employ resource usage monitoring and limits on XML parsing processes to detect and mitigate potential denial of service conditions. Regularly update software dependencies and maintain a robust vulnerability management program to quickly respond to new information or patches related to this CVE.