CVE-2023-0842 is a prototype pollution vulnerability identified in version 0.4.23 of the xml2js library, a widely used Node.js module for parsing XML into JavaScript objects. The vulnerability stems from the library's failure to properly validate JSON keys during object construction, specifically allowing the special __proto__ property to be overwritten or added. Prototype pollution occurs when an attacker manipulates the prototype of a base object, thereby affecting all objects that inherit from it. In this case, an attacker can craft malicious JSON input that includes the __proto__ property, which xml2js processes without sanitization, leading to modification of the prototype chain. This can result in unexpected behavior, such as altering application logic, bypassing security checks, or causing data corruption. The vulnerability requires no authentication or user interaction and can be exploited remotely by sending malicious JSON data to an application that uses the affected xml2js version. Although it does not directly compromise confidentiality or availability, the integrity of the application can be compromised, potentially leading to further exploitation or privilege escalation depending on the application context. No public exploits have been reported yet, but the vulnerability is assigned a CVSS 3.1 score of 5.3, indicating medium severity. The underlying weakness is classified under CWE-1321, which relates to improper handling of prototype pollution in JavaScript objects.

For European organizations, the impact of CVE-2023-0842 depends largely on the extent to which xml2js version 0.4.23 is used within their software stacks, particularly in backend services processing XML or JSON data. The vulnerability allows attackers to modify the prototype of JavaScript objects, which can lead to altered application behavior, logic bypass, or data integrity issues. This can undermine trust in critical business applications, especially those handling sensitive data or performing authorization checks based on object properties. While the vulnerability does not directly expose confidential data or cause denial of service, the integrity compromise can be leveraged for further attacks, including privilege escalation or injection of malicious code paths. European sectors such as finance, healthcare, and government, which rely heavily on secure data processing, could face operational risks if vulnerable components are exploited. Additionally, organizations with public-facing APIs or services that accept XML/JSON input are at higher risk. The absence of known active exploits reduces immediate threat but does not eliminate the risk of future attacks, making timely mitigation essential.

To mitigate CVE-2023-0842, European organizations should first identify all instances of xml2js version 0.4.23 within their environments, including direct dependencies and transitive dependencies in Node.js applications. The primary recommendation is to upgrade xml2js to a version where this vulnerability is fixed; if no official patch is available, consider applying community patches or using alternative libraries that properly sanitize JSON keys. In parallel, implement strict input validation and sanitization on all incoming JSON and XML data, explicitly disallowing keys like __proto__, constructor, and prototype to prevent prototype pollution. Employ runtime monitoring and anomaly detection to identify unusual object behavior or property changes indicative of exploitation attempts. Conduct code reviews and security testing focusing on deserialization and object property handling. Additionally, restrict exposure of vulnerable services to untrusted networks and enforce least privilege principles to limit the impact of potential exploitation. Finally, maintain up-to-date threat intelligence feeds to monitor for emerging exploits targeting this vulnerability.