CVE-2026-21854 is an authentication bypass vulnerability identified in the Tarkov Data Manager, a tool used to manage item data for the game Escape from Tarkov. The vulnerability affects versions up to and including 2.0.0 and was publicly disclosed in early January 2026. The root cause is a JavaScript prototype pollution issue combined with loose equality (==) type coercion in the login endpoint. This flaw allows an unauthenticated attacker to bypass authentication checks entirely and gain full administrative privileges on the Tarkov Data Manager admin panel. The exploitation does not require any user interaction or prior authentication, making it highly accessible to remote attackers. The vulnerability impacts confidentiality, integrity, and availability since an attacker with admin access can manipulate data, disrupt services, or exfiltrate sensitive information. The vendor addressed the issue with a series of patches released on 02 January 2025, which fixed this and other related vulnerabilities. Despite no known exploits in the wild, the critical CVSS score of 9.8 reflects the ease of exploitation and the severe impact of a successful attack. The vulnerability is categorized under CWE-287 (Improper Authentication), CWE-843 (Access of Resource Using Incompatible Type), and CWE-1321 (Improper Handling of Prototype Pollution).

For European organizations, the impact of this vulnerability can be significant, especially for those involved in gaming, software development, or digital asset management using the Tarkov Data Manager. An attacker exploiting this flaw can gain full administrative control, leading to unauthorized data manipulation, theft of sensitive information, disruption of services, and potential lateral movement within the network. This can result in operational downtime, reputational damage, and regulatory compliance issues under GDPR due to potential data breaches. The critical nature of the vulnerability means that even organizations with limited exposure to the tool could face severe consequences if exploited. Additionally, the lack of required authentication or user interaction lowers the barrier for attackers, increasing the likelihood of exploitation if systems remain unpatched.

European organizations should immediately verify if they are running Tarkov Data Manager versions 2.0.0 or earlier and upgrade to the patched version released after 02 January 2025. If upgrading is not immediately possible, restrict network access to the Tarkov Data Manager admin panel using firewalls or VPNs to limit exposure to trusted users only. Implement strict monitoring and logging of access attempts to detect any unauthorized activity. Conduct code reviews and penetration testing focused on prototype pollution and authentication mechanisms in JavaScript-based applications. Educate development teams about the risks of loose equality checks and prototype pollution vulnerabilities to prevent similar issues in future software. Finally, maintain an incident response plan tailored to quickly address potential exploitation of this vulnerability.