CVE-2019-2393 in MongoDB
Summary
by MITRE • 11/23/2020
A user authorized to perform database queries may trigger denial of service by issuing specially crafted queries, which use $lookup and collations. This issue affects: MongoDB Inc. MongoDB Server v4.2 versions prior to 4.2.1; v4.0 versions prior to 4.0.13; v3.6 versions prior to 3.6.15.
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Analysis
by VulDB Data Team • 09/17/2024
The vulnerability identified as CVE-2019-2393 represents a critical denial of service flaw within MongoDB database servers that impacts multiple major versions including 3.6, 4.0, and 4.2. This vulnerability specifically targets the aggregation pipeline functionality where the $lookup stage is utilized in conjunction with collation parameters, creating a condition that allows authenticated users to craft malicious queries designed to crash database processes. The flaw stems from insufficient input validation and error handling within the aggregation framework when processing complex join operations with specific collation settings, making it particularly dangerous as it requires only legitimate database access privileges to exploit.
The technical mechanism behind this vulnerability involves the improper handling of collation specifications within the $lookup pipeline stage during aggregation operations. When a user constructs a query using $lookup with specific collation parameters, the MongoDB server fails to properly validate the combination of these elements, leading to memory corruption or resource exhaustion that ultimately results in process termination. This behavior manifests as a denial of service condition where legitimate database operations become unavailable, disrupting service continuity for all users of the affected MongoDB instances. The vulnerability is classified under CWE-20 as a weakness involving improper input validation, specifically in the context of database query processing and aggregation pipeline execution.
The operational impact of CVE-2019-2393 extends beyond simple service disruption as it affects database availability and can potentially compromise the overall system reliability of applications that depend on MongoDB for data storage and retrieval. Organizations running affected MongoDB versions face the risk of unauthorized service disruption by any authenticated user who understands the query construction patterns that trigger the vulnerability. This creates a significant risk for database administrators who must balance legitimate user access with the potential for malicious or accidental exploitation. The vulnerability's impact is particularly severe in environments where MongoDB serves as a critical backend component for web applications, content management systems, or other services where database availability directly affects business operations.
Security practitioners should immediately implement mitigations by upgrading to the patched versions of MongoDB, specifically versions 3.6.15, 4.0.13, and 4.2.1, which contain the necessary fixes to address the aggregation pipeline handling issue. Organizations should also consider implementing additional controls such as query monitoring and rate limiting for aggregation operations, particularly those involving $lookup stages with collation parameters. The mitigation strategy should include comprehensive testing of the upgrade process to ensure compatibility with existing applications while also implementing proper access controls to limit the scope of users who can execute potentially dangerous aggregation queries. Additionally, monitoring systems should be enhanced to detect unusual patterns in aggregation pipeline usage that might indicate exploitation attempts, aligning with ATT&CK technique T1499.004 for network disruption and T1070.004 for indicator removal through manipulation of log data. Organizations should also review their database access controls and implement principle of least privilege to minimize the potential impact of any successful exploitation attempts.