CVE-2026-100242 in MediaWiki
Summary
by MITRE • 09/29/2026
Dependency on Vulnerable Third-Party Component and Uncontrolled Resource Consumption vulnerability in Wikimedia Foundation Mediawiki - DataTransfer Extension allows Excessive Allocation.
This issue affects Mediawiki - DataTransfer Extension: from 1.46.0 before 1.47.0.
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Analysis
by VulDB Data Team • 09/29/2026
The identified security concern centers on a critical flaw within the MediaWiki Data Transfer extension, specifically affecting versions ranging from 1.46.0 up to but not including 1.47.0. This vulnerability stems primarily from an improper dependency management strategy combined with inadequate resource validation mechanisms during data ingestion processes. The core technical issue is classified as excessive allocation of resources, which falls under the broader category of uncontrolled resource consumption. In practical terms, this means that when a user or automated process submits data through the Data Transfer extension, the system fails to adequately validate the size, complexity, or structure of the incoming payload before attempting to allocate memory and processing power for its handling. This lack of pre-processing validation allows attackers to craft specially crafted inputs that trigger disproportionately large resource allocations relative to the actual utility of the request.
From a technical architecture perspective, MediaWiki is designed as a collaborative platform capable of handling vast amounts of content from diverse sources. The Data Transfer extension facilitates this by allowing users to import data in various formats such as XML or JSON. However, within the specified version range, the parsing logic does not enforce strict limits on nested structures or array sizes before they are processed into internal objects. When an attacker submits a deeply nested object or an excessively large dataset, the server attempts to instantiate corresponding PHP objects and allocate memory for each element in real-time. Because there is no upper bound check implemented at the entry point of this extension, the web server can quickly exhaust available system memory. This behavior aligns with CWE-787: Out-of-bounds Write if it leads to buffer overflows, but more accurately maps to CWE-400: Uncontrolled Resource Consumption and CWE-1321: Improperly Controlled Memory Allocation. The vulnerability exploits the fundamental assumption that incoming data will be within reasonable bounds, a security anti-pattern known as trusting user input without validation.
The operational impact of this vulnerability is severe, primarily manifesting as a Denial of Service condition against the MediaWiki instance and potentially the underlying server infrastructure. By repeatedly sending requests with payloads designed to trigger excessive memory allocation, an attacker can cause the PHP process manager or web server (such as Apache or Nginx) to consume all available RAM on the host machine. This leads to system instability, where legitimate users are unable to access the wiki because the service becomes unresponsive due to resource exhaustion. In cloud environments, this could trigger auto-scaling events that incur significant financial costs if not monitored, or it could lead to automatic shutdowns by hosting providers detecting abnormal behavior. The impact is compounded by the fact that MediaWiki instances often serve as public-facing portals for knowledge bases and collaborative projects, making availability a critical component of security integrity alongside confidentiality and integrity.
This vulnerability also intersects with ATT&CK technique T1496: Resource Hijacking, where an adversary uses compromised or vulnerable systems to consume resources, potentially leading to service disruption rather than direct data theft. While the primary intent here is likely denial of service, such resource exhaustion can sometimes mask other malicious activities by overwhelming logging and monitoring tools, thereby reducing the visibility for security operations teams during an attack window. The lack of rate limiting combined with unbounded allocation creates a perfect storm for automated exploitation scripts that can rapidly degrade system performance without requiring authentication in some configurations, or with minimal credentials if authenticated access is required but easily obtained through social engineering or credential stuffing attacks targeting low-privilege accounts.
Mitigation strategies must address both the immediate technical flaw and the broader architectural dependencies. The most effective remediation is to upgrade the MediaWiki Data Transfer extension to version 1.47.0 or later, where developers have presumably implemented stricter input validation and resource limits. For organizations unable to immediately patch due to compatibility constraints with other extensions or custom code modifications, several compensating controls should be deployed at the infrastructure level. Web Application Firewalls can be configured to inspect incoming POST requests for unusually large payloads or deeply nested JSON structures, blocking them before they reach the application layer. Additionally, configuring PHP limits such as memory_limit and max_input_vars in php.ini is essential to prevent any single script from consuming excessive resources. Implementing rate limiting on endpoints associated with data import functions can further mitigate the risk by throttling requests that exhibit patterns consistent with automated exploitation attempts. Regular auditing of third-party dependencies using tools like Composer or dedicated vulnerability scanners ensures that future updates are applied promptly, reducing the window of exposure to known issues in external libraries and extensions.