CVE-2025-4328 is a medium severity security vulnerability identified in the fp2952 spring-cloud-base project, specifically affecting the sendBack function within the MvcController.java file of the auth-center-provider component. The vulnerability arises from improper handling of the HTTP Referer header, which can be manipulated by an attacker to trigger an open redirect condition. Open redirect vulnerabilities occur when an application accepts untrusted input that causes it to redirect users to external, potentially malicious websites. In this case, the sendBack function does not adequately validate or sanitize the Referer argument, allowing remote attackers to craft URLs that redirect users to arbitrary destinations. This can facilitate phishing attacks, where users are tricked into visiting malicious sites that appear trustworthy due to the initial legitimate domain. The vulnerability can be exploited remotely without authentication, though user interaction is required to follow the malicious redirect. The product uses a rolling release model, so specific version numbers for patched releases are not available, complicating patch management. The CVSS 4.0 score is 5.1 (medium severity), reflecting network attack vector, low attack complexity, no privileges required, but requiring user interaction and causing limited integrity impact. No known exploits are currently reported in the wild, but public disclosure of the exploit code increases the risk of exploitation attempts.

For European organizations using the fp2952 spring-cloud-base framework, particularly those deploying the auth-center-provider component, this vulnerability poses a risk to user trust and security. Open redirects can be leveraged by attackers to conduct phishing campaigns targeting employees or customers, potentially leading to credential theft, malware infections, or fraud. While the vulnerability does not directly compromise system confidentiality or availability, the indirect consequences of successful phishing attacks can be severe, including data breaches or financial loss. Organizations in sectors with high regulatory scrutiny, such as finance, healthcare, and government, may face compliance risks if users are redirected to malicious sites via trusted applications. Additionally, the rolling release nature of the product may delay timely patching, increasing exposure. The vulnerability’s remote exploitability without authentication means attackers can target publicly accessible endpoints, increasing the attack surface. Given the widespread use of Spring Cloud frameworks in enterprise Java applications across Europe, the potential impact is significant, especially for organizations relying on this specific component for authentication and authorization services.

To mitigate CVE-2025-4328, European organizations should first identify all instances of the fp2952 spring-cloud-base framework in their environments, focusing on the auth-center-provider component. Immediate steps include implementing strict validation and sanitization of the Referer header in the sendBack function or equivalent redirect handlers. If source code modification is feasible, developers should enforce allowlists of trusted redirect URLs and reject or neutralize any untrusted input. In cases where patch releases are not yet available due to the rolling release model, organizations can apply temporary web application firewall (WAF) rules to detect and block suspicious redirect patterns involving the Referer header. Security teams should also conduct phishing awareness training to reduce the risk of user interaction with malicious redirects. Monitoring web server logs for unusual redirect activity can help detect exploitation attempts. Finally, organizations should engage with the vendor or open-source community to obtain updates or patches as soon as they are released and incorporate them promptly into their deployment pipelines.