CVE-2025-5552 is a medium-severity vulnerability affecting ChestnutCMS versions 15.0 and 15.1. The issue resides in the API endpoint located at /dev-api/groovy/exec, where improper handling of serialized data allows an attacker to perform deserialization attacks remotely. Deserialization vulnerabilities occur when untrusted data is deserialized by an application without sufficient validation, potentially enabling attackers to execute arbitrary code, manipulate application logic, or cause denial of service. In this case, the vulnerability can be exploited without user interaction and requires only low privileges (PR:L) on the system, with no authentication or user interaction needed. The CVSS 4.0 vector indicates network attack vector (AV:N), low attack complexity (AC:L), no privileges required (AT:N), no user interaction (UI:N), and limited impacts on confidentiality, integrity, and availability (VC:L, VI:L, VA:L). Although the CVSS score is 5.3 (medium), the presence of remote deserialization in an API endpoint is concerning because it can lead to remote code execution or other critical impacts if chained with other vulnerabilities. No public exploits are currently known in the wild, and no patches or vendor advisories have been linked yet. The vulnerability was published on June 4, 2025, and affects an unknown code segment within the API endpoint, which suggests the need for further code review and monitoring for exploit attempts.

For European organizations using ChestnutCMS versions 15.0 or 15.1, this vulnerability poses a risk of unauthorized remote code execution or manipulation of CMS functionality via the API endpoint. This could lead to data breaches, defacement, or disruption of web services hosted on the CMS. Given the API endpoint is exposed remotely and requires no user interaction, attackers could automate exploitation attempts, potentially impacting availability and integrity of websites or applications relying on ChestnutCMS. Organizations in sectors with high reliance on web content management, such as media, government, and e-commerce, may face operational disruptions and reputational damage. The limited impact scores in confidentiality, integrity, and availability suggest that while the vulnerability is serious, it may not lead to full system compromise without additional conditions. However, the lack of patches and public exploit code means organizations must act proactively to prevent exploitation. The medium severity rating indicates a moderate but actionable risk, especially for organizations with internet-facing ChestnutCMS deployments.

1. Immediate mitigation should include restricting access to the /dev-api/groovy/exec endpoint via network controls such as firewalls or API gateways, limiting exposure to trusted IP addresses only. 2. Disable or remove the vulnerable API endpoint if it is not essential for business operations. 3. Conduct a thorough code audit of the API endpoint and related deserialization logic to identify and remediate unsafe deserialization practices. 4. Monitor logs and network traffic for unusual or suspicious requests targeting the /dev-api/groovy/exec path. 5. Implement Web Application Firewall (WAF) rules to detect and block deserialization attack patterns. 6. Engage with the ChestnutCMS vendor or community to obtain patches or updates as soon as they become available. 7. Consider deploying runtime application self-protection (RASP) solutions to detect and prevent exploitation attempts in real time. 8. Educate development and security teams about secure deserialization practices to prevent similar vulnerabilities in future releases.