CVE-2025-61639 is a vulnerability categorized under CWE-200, indicating exposure of sensitive information to unauthorized actors within the MediaWiki software developed by the Wikimedia Foundation. The issue specifically involves program files includes/logging/ManualLogEntry.Php, includes/recentchanges/RecentChangeFactory.Php, and includes/recentchanges/RecentChangeStore.Php. These components are responsible for logging user actions and managing recent changes data within MediaWiki. The vulnerability affects all versions prior to 1.39.14, 1.43.4, and 1.44.1, meaning multiple release branches are impacted. The flaw allows an attacker to access sensitive information without requiring authentication or user interaction, but the confidentiality impact is limited, as reflected by the CVSS 4.0 score of 1.7. The attack vector is network-based with low complexity, and no privileges or user interaction are needed, but the vulnerability does not affect integrity or availability. No known exploits have been reported in the wild, suggesting limited active threat currently. The vulnerability was reserved in late 2025 and published in early 2026, indicating recent discovery and disclosure. Since MediaWiki is widely used for collaborative documentation and knowledge management, unauthorized exposure of logs or recent change data could reveal internal operational details or user activity patterns, potentially aiding further reconnaissance or social engineering attacks.

For European organizations, the primary impact of CVE-2025-61639 is the unauthorized disclosure of sensitive information stored in MediaWiki logs and recent changes. This could include metadata about user actions, edits, or system events that may reveal internal processes or user identities. While the confidentiality impact is limited, such information leakage could facilitate targeted attacks, social engineering, or privacy violations, especially in sensitive sectors such as government, education, or research institutions that rely heavily on MediaWiki for documentation. The vulnerability does not affect system integrity or availability, so direct disruption or data manipulation is unlikely. However, the exposure of sensitive operational data could undermine trust and compliance with data protection regulations like GDPR if personal data is involved. The low CVSS score and absence of known exploits suggest the immediate risk is low, but unpatched systems remain vulnerable to opportunistic attackers scanning for exposed MediaWiki instances.

To mitigate CVE-2025-61639, European organizations should promptly upgrade MediaWiki installations to versions 1.39.14, 1.43.4, 1.44.1, or later, where the vulnerability has been addressed. In environments where immediate upgrading is not feasible, administrators should restrict network access to MediaWiki instances, especially limiting access to logging and recent changes endpoints. Implement strict access controls and authentication mechanisms to prevent unauthorized users from querying sensitive logs or recent change data. Regularly audit MediaWiki configurations and logs to detect unusual access patterns. Additionally, organizations should review and sanitize any sensitive information stored in logs or recent changes to minimize exposure. Employing web application firewalls (WAFs) to monitor and block suspicious requests targeting these specific MediaWiki components can provide an additional layer of defense. Finally, maintain awareness of updates from the Wikimedia Foundation and apply security patches promptly.