CVE-2025-15438 is a deserialization vulnerability identified in PluXml, an open-source CMS, affecting all versions up to 5.8.22. The vulnerability resides in the FileCookieJar::__destruct method located in core/admin/medias.php, part of the Media Management Module. Specifically, the function improperly handles the File argument, allowing an attacker to supply crafted serialized data that is deserialized unsafely. This can lead to remote code execution or other malicious actions depending on the deserialized payload. The attack vector is network-based (AV:N), requires no user interaction (UI:N), and does not require authentication (AT:N), making it relatively easy to exploit remotely. However, the vulnerability requires high privileges (PR:H) on the system, which somewhat limits the attack surface. The CVSS 4.0 base score is 5.1, indicating medium severity, with partial impacts on confidentiality, integrity, and availability. The vendor has acknowledged the issue and prepared a patch in version 5.8.23. No known exploits are currently observed in the wild, but public disclosure increases the risk of exploitation attempts. The vulnerability’s exploitation could allow attackers to execute arbitrary code or manipulate media files, potentially compromising the CMS and underlying server.

For European organizations using PluXml, this vulnerability poses a moderate risk. Successful exploitation could lead to unauthorized code execution, data tampering, or service disruption within the CMS environment. This can result in data breaches, defacement of websites, or pivoting to internal networks. Given PluXml’s use primarily in small to medium websites and intranets, the impact may be more significant for organizations relying on it for critical content management or media handling. The vulnerability’s remote exploitability without user interaction increases the urgency for patching. Additionally, compromised CMS instances could be leveraged for phishing, malware distribution, or as footholds for broader attacks targeting European infrastructure. The medium severity reflects a balance between ease of exploitation and the requirement for elevated privileges, but the potential for damage to confidentiality, integrity, and availability remains notable.

European organizations should immediately upgrade PluXml installations to version 5.8.23 or later where the vulnerability is patched. Until patching is possible, restrict network access to the administrative media management interfaces to trusted IPs only. Implement web application firewalls (WAFs) with rules to detect and block suspicious serialized payloads or unusual requests targeting medias.php. Conduct thorough audits of existing PluXml deployments to identify vulnerable versions and remove or isolate exposed instances. Employ strict input validation and sanitization where possible, and monitor logs for anomalous deserialization attempts. Additionally, enforce the principle of least privilege on CMS user accounts and server processes to limit the impact of potential exploitation. Regularly back up CMS data and configurations to enable rapid recovery in case of compromise. Finally, maintain awareness of emerging exploit techniques related to this vulnerability to adapt defenses accordingly.