CVE-2024-50602 is a medium-severity vulnerability identified in libexpat, a widely used XML parsing library. The issue arises from improper handling of parser state transitions within the XML_ResumeParser function. Specifically, the vulnerability occurs when XML_StopParser is called on a parser instance that has not yet been started. This leads to a crash, which is indicative of a denial-of-service (DoS) condition due to improper state management. The root cause is related to CWE-754 (Improper Check for Unusual or Exceptional Conditions), where the parser does not correctly validate the parser's state before attempting to stop or suspend it. The CVSS v3.1 base score is 5.9 (medium), with the vector AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H, indicating that the vulnerability can be exploited remotely over the network without privileges or user interaction, but requires high attack complexity. The impact is limited to availability, as confidentiality and integrity are not affected. No known exploits are currently reported in the wild, and no specific vendor or product versions are detailed beyond libexpat versions prior to 2.6.4. Given libexpat's extensive use in numerous open-source and commercial applications for XML parsing, this vulnerability could potentially affect a broad range of software products that embed this library, especially those that handle XML input from untrusted sources and may invoke parser stop/resume operations dynamically. The lack of a patch link suggests that remediation may require updating to libexpat 2.6.4 or later once available. Overall, this vulnerability represents a denial-of-service risk through application crashes triggered by malformed or unexpected XML parsing control sequences.

For European organizations, the primary impact of CVE-2024-50602 is the risk of denial-of-service conditions in applications relying on libexpat for XML parsing. This could disrupt services, especially in environments where XML is used extensively for configuration, data interchange, or communication protocols. Industries such as finance, telecommunications, manufacturing, and government services that utilize XML-based workflows or APIs may experience service interruptions or degraded availability. Although the vulnerability does not compromise data confidentiality or integrity, availability disruptions can lead to operational downtime, loss of productivity, and potential cascading effects in critical infrastructure systems. Given the medium severity and high attack complexity, exploitation is less straightforward but remains a concern for systems exposed to untrusted network inputs. The absence of known exploits reduces immediate risk but does not eliminate the need for proactive mitigation, especially in sectors with stringent uptime requirements or regulatory compliance obligations related to service availability.

Update libexpat to version 2.6.4 or later as soon as the patch is available to ensure the vulnerability is addressed at the library level. Conduct an inventory of all software and systems that embed libexpat, including indirect dependencies, to identify potentially affected applications. Implement input validation and sanitization for XML data, particularly ensuring that XML parsing control functions such as stop/resume are not invoked on uninitialized parsers. Where possible, configure XML parsers to operate in safe modes that prevent suspension or stopping of parsers before they start, or add application-level checks to prevent such states. Deploy runtime monitoring and anomaly detection to identify unusual parser crashes or service disruptions that may indicate exploitation attempts. In critical environments, consider isolating XML parsing components to limit the impact of crashes, such as running parsers in sandboxed or containerized environments. Engage with software vendors and open-source communities to track patch releases and apply updates promptly. Review and update incident response plans to include scenarios involving denial-of-service via XML parser crashes.