CVE-2025-61766 is a vulnerability classified under CWE-674 (Uncontrolled Recursion) found in the weirdgloop MediaWiki extension named 'Bucket', which is designed to store and retrieve structured data on MediaWiki articles. In versions prior to 1.0.0, the extension improperly handles queries using the '!=' comparator, leading to infinite recursion. When such a query is executed, the PHP interpreter's call stack grows uncontrollably until it exceeds the configured limit, causing a fatal error or crash. Additionally, the recursion causes excessive memory consumption, which can degrade system performance or cause the MediaWiki instance to become unresponsive. This vulnerability does not expose or modify data (no confidentiality or integrity impact) but results in a denial of service by making the service unavailable or unstable. Exploitation requires an authenticated user with permission to query buckets, but no further user interaction is necessary beyond issuing the malicious query. The vulnerability was publicly disclosed on October 6, 2025, with a CVSS v3.1 score of 6.5 (medium severity), reflecting its network attack vector, low attack complexity, and requirement for privileges but no user interaction. The issue is resolved in version 1.0.0 of the extension, which includes a patch to prevent infinite recursion by properly handling the '!=' comparator in queries.

For European organizations, the primary impact of CVE-2025-61766 is the potential denial of service on MediaWiki platforms using the vulnerable 'Bucket' extension. This can disrupt internal knowledge bases, documentation portals, or public-facing wikis, affecting business continuity and operational efficiency. Organizations relying on MediaWiki for collaborative content management, especially in government, education, and research sectors, may experience outages or degraded performance, impacting user productivity and service availability. Since the vulnerability requires authenticated access, insider threats or compromised user accounts could be leveraged to exploit this issue. While no data breach or integrity compromise is expected, the loss of availability could hinder critical workflows and damage organizational reputation. The absence of known exploits in the wild currently reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits following public disclosure. European entities with strict uptime and service availability requirements must prioritize mitigation to avoid operational disruptions.

To mitigate CVE-2025-61766, European organizations should immediately upgrade the weirdgloop MediaWiki 'Bucket' extension to version 1.0.0 or later, where the infinite recursion issue is patched. If upgrading is not immediately feasible, organizations should restrict access to the bucket query functionality to trusted users only, implementing strict access controls and monitoring query usage for anomalous patterns. Employing web application firewalls (WAFs) with custom rules to detect and block queries using the '!=' comparator in bucket queries can provide temporary protection. Additionally, organizations should audit user privileges to minimize the number of users able to perform such queries, enforce strong authentication mechanisms, and monitor MediaWiki logs for signs of exploitation attempts. Regular backups and incident response plans should be updated to handle potential DoS incidents. Finally, staying informed on updates from the vendor and applying patches promptly is critical to maintaining security.