Chamilo LMS, a widely used open-source learning management system, suffered from a critical deserialization vulnerability identified as CVE-2025-52998 (CWE-502). Prior to version 1.11.30, the application deserializes data without sufficient validation or sanitization, allowing attackers to supply crafted serialized objects. This enables the creation of arbitrary class instances with attacker-controlled properties, effectively allowing manipulation of the application's internal logic and state. Such deserialization flaws can lead to remote code execution, privilege escalation, or application logic corruption depending on the classes available and their methods. The vulnerability does not require user interaction but does require the attacker to have high privileges, indicating that exploitation might be limited to authenticated users with elevated rights or through chained attacks. The CVSS 4.0 base score is 7.0 (high), reflecting network attack vector, low attack complexity, no user interaction, and high impact on availability and integrity, with limited impact on confidentiality. The flaw was publicly disclosed and patched in Chamilo LMS version 1.11.30. No public exploits have been reported yet, but the risk remains significant due to the potential for severe application disruption and logic manipulation.

The vulnerability allows attackers to manipulate the internal logic of Chamilo LMS by injecting arbitrary objects during deserialization. This can lead to unauthorized changes in application behavior, potentially causing data corruption, denial of service, or privilege escalation within the LMS environment. Educational institutions and organizations relying on Chamilo LMS for critical learning services could face service outages or compromised data integrity. Since the flaw requires high privileges, the immediate risk is to users or attackers who have already gained elevated access, but it could be leveraged as part of a multi-stage attack to escalate privileges or disrupt operations. The availability impact is high, as the application logic can be altered to cause crashes or denial of service. Integrity is also highly affected due to the possibility of unauthorized data or state manipulation. Confidentiality impact is limited but not negligible if deserialization leads to exposure of sensitive data indirectly. The lack of user interaction requirement and network attack vector means the vulnerability can be exploited remotely once the attacker has sufficient privileges.

Organizations should immediately upgrade Chamilo LMS to version 1.11.30 or later, where the vulnerability is patched. In addition to patching, administrators should audit all deserialization processes in the application to ensure they only deserialize trusted data and implement strict input validation and allowlisting of classes during deserialization. Employing application-layer firewalls or runtime application self-protection (RASP) solutions can help detect and block malicious serialized payloads. Restricting user privileges to the minimum necessary reduces the risk of exploitation by limiting the pool of users who can trigger the vulnerability. Regularly monitoring logs for unusual deserialization activity or application errors can provide early warning signs of exploitation attempts. Finally, educating developers and administrators about secure coding practices related to serialization and deserialization is critical to prevent similar vulnerabilities.