CVE-2026-82055 in MongoDB
Summary
by MITRE • 09/08/2026
A security issue exists in MongoDB's 2dsphere index key generation that can cause a server crash due to a null pointer dereference. When a specially crafted GeoJSON document is inserted into a collection with a 2dsphere index, an inconsistency in geometry parsing can leave an internal object in an invalid, partially initialized state. During subsequent index key generation, access to this improperly initialized object results in a null pointer dereference that terminates the mongod process. An authenticated user with write access can use this to cause a denial of service.
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Analysis
by VulDB Data Team • 09/08/2026
The vulnerability identified in MongoDB involves a critical flaw within the 2dsphere index key generation mechanism, specifically triggered by the processing of GeoJSON documents. This issue stems from an inconsistency in how geometry data is parsed and validated before being incorporated into the internal database structures. When a specially crafted GeoJSON document containing malformed or edge-case geometric coordinates is inserted into a collection that has a 2dsphere index defined, the server fails to properly initialize certain internal objects associated with that geometry. Instead of rejecting the invalid input gracefully, MongoDB proceeds with an incomplete state for these internal representations. This partial initialization leaves critical pointers unset or null, creating a latent defect within the database engine's memory management logic during the indexing phase.
The operational impact manifests when the server attempts to generate index keys for this improperly initialized object. During this process, the application logic assumes that all necessary geometric data structures are fully populated and valid. However, due to the earlier parsing inconsistency, specific pointers remain null. When the code executes a dereference operation on these null pointers to extract coordinate or topology information required for key generation, it triggers a segmentation fault. This results in an immediate termination of the mongod process, effectively crashing the database instance. The crash is deterministic and repeatable given the same malicious input, making this vulnerability highly exploitable by any actor who can interact with the affected index structure.
From a security perspective, this flaw represents a significant denial of service risk for MongoDB deployments that utilize geospatial indexing capabilities. While the exploitation requires an authenticated user with write access to the specific collection, this is often achievable in environments where application-level authentication does not strictly enforce least-privilege principles or when credentials are compromised through other vectors such as weak passwords or exposed administrative ports. The ability of a single authenticated user to crash the entire database server undermines the availability pillar of the CIA triad and can lead to significant operational downtime, data unavailability, and potential loss of trust in the system's reliability.
This vulnerability aligns with CWE-476, which describes a NULL Pointer Dereference, as the root cause is the access of memory through an uninitialized or null pointer. In terms of offensive security frameworks, this behavior corresponds to MITRE ATT&CK technique T1529, System Shutdown/Reboot, specifically under the subcategory of service stop via crash exploitation. Attackers leverage such flaws to disrupt services without needing elevated privileges beyond basic write access, making it a potent tool for denial-of-service attacks in multi-tenant or poorly segmented database environments.
To mitigate this risk, administrators should ensure that MongoDB instances are updated to versions where the geometry parsing logic has been hardened against malformed inputs. The fix typically involves adding robust validation checks before attempting to initialize internal geometric objects and ensuring that null pointers are handled gracefully rather than causing a crash. Additionally, implementing strict input validation at the application layer can prevent maliciously crafted GeoJSON documents from reaching the database engine in the first place. Network-level controls should also be reviewed to ensure that MongoDB ports are not exposed to untrusted networks, thereby reducing the attack surface for authenticated users who might attempt such exploits. Regular auditing of user privileges and enforcing strict role-based access control further limits the potential impact by restricting write access only to those applications or users that absolutely require it.