CVE-2025-62379 is classified as a CWE-601 (Open Redirect) vulnerability found in the reflex Python library, which is used for building full-stack web applications. The vulnerability exists in versions 0.5.4 through 0.8.14 within the /auth-codespace endpoint. This endpoint reads the redirect_to query parameter and assigns its value directly to the href attribute of a client-side anchor element without any validation or sanitization. Immediately after assignment, the code programmatically triggers a click event on this link, causing automatic navigation to the specified URL. The endpoint is conditionally registered only when the environment is detected as a GitHub Codespaces environment, controlled by environment variables such as GITHUB_CODESPACES_PORT_FORWARDING_DOMAIN. If this environment variable is set in production, the vulnerability can be exploited outside Codespaces. The detection mechanism relies on a sessionStorage flag, causing the redirect to trigger on first visits or in incognito/private browsing modes. There is no server-side whitelist or origin enforcement, allowing arbitrary external URLs to be targeted. This vulnerability can be exploited by attackers to redirect users to malicious sites, facilitating phishing, credential theft, or malware delivery. The vulnerability does not impact confidentiality directly but can lead to indirect risks through social engineering. It requires user interaction (page load and automatic click) and has a CVSS v3.1 score of 3.1 (low severity). The issue was fixed in reflex version 0.8.15. As a mitigation, users should avoid setting the GITHUB_CODESPACES_PORT_FORWARDING_DOMAIN environment variable in production environments.

For European organizations, the primary risk posed by this vulnerability is the potential for phishing and social engineering attacks leveraging the open redirect to lure users to malicious websites. This can lead to credential compromise, malware infections, or unauthorized access if users are tricked into providing sensitive information or downloading harmful content. Although the vulnerability itself does not directly compromise system confidentiality or availability, the indirect consequences can be significant, especially for organizations with employees or customers using reflex-based applications in GitHub Codespaces or production environments where the vulnerable configuration exists. The automatic redirection without user awareness increases the risk of successful exploitation. Organizations relying on reflex in development or production should be aware that attackers could exploit this flaw to undermine user trust and potentially escalate attacks. However, the low CVSS score and requirement for user interaction limit the overall severity. The threat is more relevant to organizations with a strong presence in software development using GitHub Codespaces or reflex-based deployments.

1. Upgrade reflex to version 0.8.15 or later, where the vulnerability is patched. 2. In production environments, ensure that the environment variable GITHUB_CODESPACES_PORT_FORWARDING_DOMAIN is not set or removed to prevent activation of the vulnerable endpoint. 3. Implement strict input validation and sanitization for any redirect parameters, enforcing a whitelist of allowed domains or internal paths to prevent open redirects. 4. Educate users and developers about the risks of open redirects and encourage vigilance against suspicious URLs, especially those originating from reflex-based applications. 5. Monitor web application logs for unusual redirect_to parameter usage or unexpected redirection patterns. 6. If upgrading is not immediately possible, consider disabling or restricting access to the /auth-codespace endpoint in production environments. 7. Incorporate Content Security Policy (CSP) headers to restrict navigation to trusted domains, mitigating the impact of malicious redirects. 8. Conduct security reviews of environment variable configurations to avoid accidental exposure of Codespaces-specific variables in production.