CVE-2025-53021 is a medium-severity session fixation vulnerability impacting Moodle versions 3.x through 3.11.18. This vulnerability allows unauthenticated attackers to hijack user sessions via the sesskey parameter. The sesskey can be obtained without authentication and reused within the OAuth2 login flow, resulting in the victim's session being linked to the attacker's. Successful exploitation results in full account takeover. According to the Moodle Releases page, "Bug fixes for security issues in 3.11.x ended 11 December 2023." Notably, this vulnerability only affects products that are no longer supported by the maintainer.
The vulnerability has a CVSS score of 4.2, which signifies a medium risk level. This score reflects the potential for attackers to exploit the vulnerability through a network attack vector with high complexity. The attack requires user interaction, highlighting the importance of user awareness in mitigating the risk involved.
Organizations using the affected versions of Moodle should take immediate action as the exploitation could lead to significant security breaches, including unauthorized access to sensitive user data. The urgency for defenders is heightened due to the nature of the vulnerability and its impact on user session integrity.
Given that this vulnerability affects unsupported versions, organizations should assess their current deployments and prioritize patching to supported versions to ensure continued security and support against potential exploits.
The risk to organizations includes potential account takeover and unauthorized access to user data, emphasizing the necessity of proactive security measures.
Vulnerability Details
CVE-2025-53021 is classified as a session fixation vulnerability. The CVSS 3.1 score of 4.2 indicates a medium severity level, which suggests that while the exploitability may not be trivial, the consequences can be severe if successfully executed. The affected product is Moodle, specifically versions from 3.0.0 to 3.11.18. The vulnerability was published on June 24, 2025, and the weakness is categorized under CWE-384.
Technical Analysis
The root cause of the vulnerability lies in the handling of the sesskey parameter within the OAuth2 login flow. Attackers may exploit this by obtaining a valid sesskey and manipulating user sessions. The attack vector is network-based, requiring a high level of complexity due to the need for user interaction, as the session must be established by the victim. Privileges required for this attack are none, making it particularly concerning for users.
Risk & Impact Analysis
The real-world deployment risk associated with this vulnerability is significant. Organizations using unsupported versions of Moodle face a heightened risk of account takeover due to their inability to receive security patches. This vulnerability could have a broad impact, especially in environments where sensitive information is handled through user accounts. The urgency of addressing this vulnerability is moderate, as organizations should schedule remediation in their patch cycle.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The following versions of Moodle are affected by this vulnerability: all versions from 3.0.0 to 3.11.18. Organizations should be aware that this vulnerability specifically impacts products that are no longer supported by the maintainer.
Mitigation & Remediation
For further information, organizations can explore additional resources such as the vulnerability management program, insights into penetration testing methodology, and the importance of API security best practices in safeguarding against vulnerabilities.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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