CVE-2026-8063 in Server
Summary
by MITRE • 05/07/2026
An authenticated user can crash mongod when running $rankFusion or $scoreFusion with an empty pipeline on a view.
When resolving a view, the server inspects the aggregation pipeline to determine whether it begins with an Atlas Search stage. For $rankFusion and $scoreFusion, this inspection reads the first element on each stage’s input pipeline array without first verifying that the array is non-empty. Supplying an empty pipeline causes a null pointer dereference and crashes the server.
This issue affects MongoDB Server 8.2 versions prior to 8.2.7.
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Analysis
by VulDB Data Team • 05/10/2026
This vulnerability represents a critical denial of service condition in MongoDB Server versions prior to 8.2.7, specifically impacting the aggregation framework's view resolution mechanism. The flaw occurs when an authenticated user executes aggregation operations using $rankFusion or $scoreFusion stages with empty pipeline arrays. The server's view resolution process performs preliminary checks to identify Atlas Search stages at the beginning of aggregation pipelines, but fails to validate array contents before accessing them. This oversight creates a null pointer dereference condition that terminates the mongod process, effectively crashing the database server and disrupting all connected applications and services.
The technical implementation of this vulnerability stems from inadequate input validation within MongoDB's internal aggregation pipeline processing logic. When the server encounters a view definition containing $rankFusion or $scoreFusion stages, it attempts to inspect the pipeline array for Atlas Search stage indicators by directly accessing the first element without confirming the array's existence or non-emptiness. This primitive memory access pattern violates fundamental defensive programming practices and creates a direct path to memory corruption. The vulnerability maps to CWE-476 Null Pointer Dereference, which is classified as a high-severity weakness in the Common Weakness Enumeration catalog, specifically targeting scenarios where null references are dereferenced without proper validation.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be exploited by authenticated users to cause persistent database outages that may require manual intervention and server restarts. Database administrators face the challenge of maintaining service availability while the system recovers from crashes, potentially leading to data consistency issues and extended downtime for applications dependent on MongoDB. The vulnerability affects MongoDB Server 8.2 versions prior to 8.2.7, indicating that this was a recently introduced flaw in the aggregation pipeline processing that was subsequently patched. Attackers with valid credentials can leverage this weakness to cause repeated service interruptions, making it particularly dangerous in production environments where database stability is paramount.
Mitigation strategies for this vulnerability should prioritize immediate patching to MongoDB Server 8.2.7 or later versions where the null pointer dereference has been addressed. Organizations should implement network segmentation to limit access to MongoDB instances and employ principle of least privilege to restrict user authentication credentials. Additionally, monitoring systems should be enhanced to detect unusual aggregation patterns and potential exploitation attempts. The fix implemented by MongoDB developers involves adding proper array length validation before accessing pipeline elements, which aligns with ATT&CK technique T1499.004 for avoiding detection through system disruption. Security teams should also consider implementing database activity monitoring and alerting mechanisms to proactively identify and respond to potential exploitation attempts targeting this specific vulnerability.