CVE-2025-32962 is a medium-severity vulnerability classified as CWE-601 (URL Redirection to Untrusted Site, commonly known as an open redirect) affecting the Flask-AppBuilder framework versions prior to 4.6.2. Flask-AppBuilder is a popular application development framework built on top of Flask, widely used for creating web applications with integrated security and user management features. The vulnerability arises because the affected versions do not properly validate the Host header in incoming HTTP requests, allowing an unauthenticated attacker to craft malicious URLs that redirect users to arbitrary external domains. This can be exploited by manipulating the Host header to cause the application to redirect users to untrusted sites, potentially facilitating phishing attacks, credential theft, or distribution of malware. The vulnerability does not require any authentication but does require user interaction (clicking on a crafted link). The impact on confidentiality is limited to potential user information disclosure through phishing, with no direct impact on integrity or availability. The vulnerability was addressed in Flask-AppBuilder version 4.6.2 by introducing the `FAB_SAFE_REDIRECT_HOSTS` configuration variable, which allows administrators to explicitly specify trusted domains for redirection, thereby preventing open redirects. As an interim mitigation, deploying a reverse proxy to enforce trusted Host headers can help prevent exploitation. No known exploits are currently reported in the wild, but the vulnerability's nature makes it a candidate for social engineering attacks if left unpatched. The CVSS v3.1 base score is 4.3, reflecting its medium severity with network attack vector, low attack complexity, no privileges required, but requiring user interaction and limited confidentiality impact.

For European organizations, the primary risk posed by this vulnerability is the facilitation of phishing and social engineering attacks leveraging trusted web applications built on Flask-AppBuilder. Attackers could redirect users to malicious sites that mimic legitimate services, potentially leading to credential compromise or malware infection. This risk is particularly relevant for organizations that use Flask-AppBuilder for internal portals, dashboards, or customer-facing applications. While the vulnerability does not directly compromise system integrity or availability, successful phishing attacks can lead to broader security incidents including unauthorized access or data breaches. The medium severity indicates that while the vulnerability is not critical, it should not be ignored, especially in sectors with high security requirements such as finance, healthcare, and government. European organizations must consider the regulatory implications under GDPR if user data is compromised as a result of phishing attacks exploiting this vulnerability.

1. Upgrade Flask-AppBuilder to version 4.6.2 or later immediately to benefit from the built-in mitigation using the `FAB_SAFE_REDIRECT_HOSTS` configuration. 2. Configure `FAB_SAFE_REDIRECT_HOSTS` to explicitly list only trusted domains allowed for redirection, minimizing the risk of open redirects. 3. If immediate upgrade is not feasible, deploy a reverse proxy or web application firewall (WAF) in front of Flask-AppBuilder applications to validate and enforce trusted Host headers, blocking requests with suspicious or untrusted Host values. 4. Conduct user awareness training to recognize phishing attempts that may exploit open redirect vulnerabilities. 5. Monitor application logs for unusual redirect patterns or suspicious Host header values that could indicate attempted exploitation. 6. Review and restrict any URL redirection logic in custom application code built on Flask-AppBuilder to ensure it does not allow arbitrary redirects. 7. Implement Content Security Policy (CSP) headers to reduce the impact of malicious redirects by restricting the domains to which browsers can navigate or load resources.