CVE-2024-21336 is a security vulnerability identified in the Chromium-based Microsoft Edge browser, classified under CWE-357, which refers to Insufficient UI Warning of Dangerous Operations. This vulnerability involves the browser's user interface failing to provide adequate warnings to users when potentially dangerous operations are initiated, specifically enabling spoofing attacks. Spoofing in this context means an attacker could craft a deceptive UI element or manipulate the browser's interface to mislead users into believing they are interacting with a legitimate or safe operation, while in reality, they might be tricked into performing unintended actions. The vulnerability affects version 1.0.0 of Microsoft Edge (Chromium-based). The CVSS v3.1 base score is 2.5, indicating a low severity level. The vector string (AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N/E:U/RL:O/RC:C) reveals that the attack requires local access (AV:L), high attack complexity (AC:H), no privileges required (PR:N), and user interaction (UI:R). The impact is limited to integrity (I:L) with no confidentiality or availability impact. There are no known exploits in the wild, and no patches have been linked yet. The vulnerability was published on January 26, 2024, and was reserved in December 2023. The insufficient UI warning could allow attackers with local access to trick users into performing actions that could alter data or settings, but the high complexity and requirement for user interaction limit the exploitability and impact.

For European organizations, the impact of CVE-2024-21336 is relatively low due to the vulnerability's limited scope and low severity score. However, organizations with high security requirements or those handling sensitive data should be aware that this vulnerability could be leveraged in targeted local attacks, especially in environments where users have physical or local access to devices running the affected Microsoft Edge version. The spoofing aspect could lead to unauthorized changes or manipulation of browser settings or data integrity issues if users are deceived. This might be more concerning in sectors such as finance, government, or critical infrastructure where even minor integrity breaches could have cascading effects. Since exploitation requires local access and user interaction, remote exploitation or large-scale attacks are unlikely, reducing the overall risk to most organizations. Nonetheless, awareness and mitigation are important to prevent potential insider threats or attacks involving social engineering.

To mitigate this vulnerability effectively, European organizations should: 1) Ensure that all Microsoft Edge installations are updated to the latest version beyond 1.0.0 where this vulnerability is addressed, or monitor for official patches from Microsoft and apply them promptly once available. 2) Implement strict local access controls and endpoint security measures to prevent unauthorized physical or local access to devices, including enforcing strong authentication and session locking policies. 3) Educate users about the risks of spoofing and the importance of verifying UI prompts before taking actions, especially when prompted by the browser for sensitive operations. 4) Employ application whitelisting and endpoint detection and response (EDR) tools to monitor for suspicious local activities that could indicate attempts to exploit UI spoofing. 5) Consider using browser security configurations or extensions that enhance UI integrity and alert users to suspicious UI behaviors. 6) Regularly audit and review browser configurations and user permissions to minimize the attack surface related to local user actions.