CVE-2015-8001 in MediaWiki
Summary
by MITRE
The chunked upload API (ApiUpload) in MediaWiki before 1.23.11, 1.24.x before 1.24.4, and 1.25.x before 1.25.3 does not restrict the uploaded data to the claimed file size, which allows remote authenticated users to cause a denial of service via a chunk that exceeds the file size.
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Analysis
by VulDB Data Team • 06/25/2022
The vulnerability CVE-2015-8001 affects MediaWiki's chunked upload API implementation, specifically within the ApiUpload functionality that handles file uploads in segmented chunks. This flaw exists in MediaWiki versions prior to 1.23.11, 1.24.4, and 1.25.3 respectively, representing a critical security gap in the platform's file handling mechanisms. The vulnerability stems from insufficient validation of chunked upload data where the system fails to enforce proper bounds checking between the claimed file size and the actual data received during the upload process. This oversight allows malicious actors to manipulate the upload process by sending chunks that exceed the specified file size limits, creating a potential vector for resource exhaustion attacks.
The technical implementation flaw manifests in the chunked upload API's failure to maintain proper data integrity checks during the upload process. When users initiate a chunked file upload, MediaWiki typically accepts multiple chunks and reconstructs them into a complete file. However, the vulnerability occurs because the system does not validate that each chunk's data does not exceed the remaining space allocated for the file based on the initial file size declaration. This creates a scenario where an authenticated user can send oversized chunks that, when aggregated, cause the system to consume excessive memory or storage resources, leading to denial of service conditions.
From an operational impact perspective, this vulnerability enables authenticated attackers to consume system resources and potentially cause service disruption without requiring elevated privileges beyond standard user access. The denial of service occurs through resource exhaustion mechanisms where the server allocates memory or storage space for what it believes to be a smaller file, but receives data that exceeds these allocations. This can lead to memory exhaustion, disk space depletion, or process starvation, effectively making the MediaWiki service unavailable to legitimate users. The vulnerability is particularly concerning because it requires only authenticated access, meaning any user with valid credentials can exploit it to impact system availability.
The vulnerability maps to CWE-400, which addresses "Uncontrolled Resource Consumption" and aligns with ATT&CK technique T1499.1, "Storage Exhaustion Flood" in the context of denial of service attacks. The attack vector operates through the legitimate chunked upload API functionality, making it difficult to distinguish between normal and malicious usage patterns. Organizations using affected MediaWiki versions face significant operational risks as this vulnerability can be exploited to cause cascading failures in web services that depend on MediaWiki for content management. The impact extends beyond simple service disruption to potential data integrity concerns, as the system may fail to properly handle or validate the corrupted upload process.
Mitigation strategies should focus on immediate software updates to patched MediaWiki versions that include proper bounds checking for chunked uploads. Additionally, administrators should implement rate limiting and upload size restrictions at the network level to prevent excessive resource consumption. The recommended approach involves applying the official security patches provided by the MediaWiki project, which address the core validation logic to ensure that chunked upload data cannot exceed the declared file size limits. Network monitoring should be enhanced to detect unusual upload patterns, and system administrators should establish alerts for resource consumption spikes that may indicate exploitation attempts. Regular security audits of file upload mechanisms and implementation of proper input validation controls should be part of ongoing security maintenance practices.