CVE-2022-23990 is a high-severity vulnerability affecting Expat (also known as libexpat), an open-source XML parser library widely used in numerous software applications and systems. The vulnerability exists in versions of Expat prior to 2.4.4 and is caused by an integer overflow in the doProlog function. This function is responsible for processing the prolog section of XML documents, which includes declarations and processing instructions before the root element. An integer overflow in this context means that the function incorrectly handles certain input sizes or lengths, causing an arithmetic overflow that can lead to memory corruption or unexpected behavior. According to the CVSS v3.1 vector (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H), the vulnerability can be exploited remotely over the network without any privileges or user interaction, and it impacts availability but not confidentiality or integrity. This suggests that an attacker could craft a malicious XML document that, when parsed by a vulnerable version of Expat, triggers the overflow and causes a denial-of-service (DoS) condition, such as a crash or resource exhaustion. Although no known exploits have been reported in the wild, the vulnerability's characteristics make it a significant risk, especially for systems that rely on Expat for XML parsing in network-facing applications or services. The lack of a vendor or product name in the provided data indicates that the vulnerability is in the library itself rather than a specific product, meaning any software embedding vulnerable versions of Expat could be affected. The CWE-190 classification confirms the root cause as an integer overflow, a common programming error leading to security issues.

For European organizations, the impact of CVE-2022-23990 primarily involves potential service disruption due to denial-of-service attacks. Many European enterprises, government agencies, and critical infrastructure providers use software that incorporates Expat for XML processing, including web servers, middleware, network appliances, and embedded systems. A successful exploitation could cause application crashes or unavailability, impacting business continuity, customer services, and operational technology systems. While the vulnerability does not directly compromise data confidentiality or integrity, the resulting downtime could have cascading effects, such as delayed transactions, loss of productivity, or failure of automated processes. In sectors like finance, healthcare, telecommunications, and public administration, even temporary outages can have significant regulatory and reputational consequences. Moreover, the ease of remote exploitation without authentication or user interaction increases the risk of opportunistic attacks or automated scanning targeting vulnerable systems across Europe. Organizations relying on third-party software that bundles Expat should be aware that their exposure depends on the update cycle of those vendors.

To mitigate CVE-2022-23990 effectively, European organizations should: 1) Identify all software and systems that use Expat for XML parsing, including embedded devices and third-party applications. 2) Verify the version of Expat in use and prioritize upgrading to version 2.4.4 or later, where the integer overflow has been fixed. 3) If immediate upgrading is not feasible, implement network-level protections such as Web Application Firewalls (WAFs) or Intrusion Prevention Systems (IPS) that can detect and block malformed XML payloads or anomalous traffic patterns targeting XML parsers. 4) Conduct thorough testing of XML input validation and parsing routines in custom or in-house applications to ensure they handle edge cases safely. 5) Monitor logs and network traffic for signs of repeated XML parsing errors or crashes that could indicate exploitation attempts. 6) Engage with software vendors to confirm their patching status and request updates if they embed vulnerable Expat versions. 7) Incorporate this vulnerability into incident response and vulnerability management workflows to ensure timely detection and remediation. These steps go beyond generic advice by emphasizing inventory, vendor coordination, and layered defenses tailored to XML parsing risks.