CVE-2024-6839 identifies a vulnerability in the corydolphin/flask-cors library version 4.0.1 related to improper resolution of path equivalence (CWE-41). The root cause is the plugin's regex matching logic, which prioritizes longer regex patterns over more specific ones when determining which CORS policy to apply to incoming requests. This behavior can cause less restrictive CORS policies to be applied to sensitive endpoints unintentionally. Since CORS policies control which origins can access resources cross-origin, this flaw can lead to unauthorized origins gaining access to sensitive data or functionality that should be restricted. The vulnerability does not require authentication but does require user interaction, such as a victim visiting a malicious website that triggers cross-origin requests. The CVSS 3.0 base score is 4.3 (medium severity), reflecting low confidentiality impact, no integrity or availability impact, network attack vector, low attack complexity, no privileges required, and user interaction required. No patches or exploits are currently reported, but the risk lies in potential data exposure and unauthorized actions via cross-origin requests. Organizations using flask-cors should audit their regex-based CORS configurations and consider applying stricter, more precise patterns or alternative CORS management solutions.

For European organizations, this vulnerability can lead to unauthorized cross-origin access to sensitive web application endpoints, potentially exposing confidential user data or internal functionality. This exposure increases the risk of data breaches, privacy violations under GDPR, and unauthorized operations that could disrupt business processes or compromise user trust. Since flask-cors is commonly used in Python-based web applications, organizations relying on this library for CORS management are at risk if they use vulnerable versions and have complex regex patterns for path matching. The impact is particularly significant for sectors handling sensitive personal or financial data, such as finance, healthcare, and government services. Although the vulnerability does not directly affect system integrity or availability, the confidentiality breach and potential for unauthorized actions pose compliance and reputational risks. The medium severity rating suggests that while exploitation is feasible, the overall damage is limited to confidentiality and requires user interaction.

To mitigate CVE-2024-6839, European organizations should: 1) Immediately audit all flask-cors configurations focusing on regex path patterns to ensure that more specific patterns are prioritized correctly and no overly permissive patterns exist. 2) Where possible, replace regex-based path matching with explicit allowlists or exact path matching to avoid ambiguity. 3) Monitor cross-origin requests and CORS headers in production environments to detect anomalous or unauthorized access attempts. 4) Stay alert for official patches or updates from the corydolphin/flask-cors project and apply them promptly once available. 5) Educate developers on secure CORS configuration best practices, emphasizing the risks of improper regex prioritization. 6) Consider implementing additional application-layer access controls to sensitive endpoints beyond CORS policies. 7) Use web application firewalls (WAFs) to block suspicious cross-origin requests if feasible. These steps go beyond generic advice by focusing on regex pattern auditing and layered security controls specific to this vulnerability.