CVE-2026-18688 in MongoDB
Summary
by MITRE • 08/11/2026
An issue in MongoDB Server's aggregation framework could allow an authenticated user to trigger an out-of-bounds memory read by providing a specially formed numeric parameter in a certain aggregation pipeline stage. This could result in a server crash (denial of service) and may potentially expose a limited amount of memory contents.
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Analysis
by VulDB Data Team • 08/11/2026
This vulnerability resides within the MongoDB Server's aggregation framework, representing a critical security flaw that affects authenticated users with access to database operations. The issue manifests when a specially crafted numeric parameter is introduced into specific aggregation pipeline stages, creating conditions that lead to out-of-bounds memory reads. Such vulnerabilities fall under the category of memory safety issues and are classified as CWE-125: Out-of-bounds Read according to the Common Weakness Enumeration catalog. The aggregation framework serves as a powerful data processing engine within MongoDB, enabling complex operations like filtering, grouping, and transforming data sets through pipeline stages that process documents sequentially.
The technical exploitation of this vulnerability occurs when an authenticated user constructs malicious aggregation queries containing malformed numeric parameters that cause the server's memory management system to access memory locations beyond allocated boundaries. This out-of-bounds memory access typically results in undefined behavior including segmentation faults, server crashes, and subsequent denial of service conditions that render the database instance unavailable to legitimate users. The vulnerability's impact extends beyond simple service disruption as it may potentially expose sensitive memory contents to the attacker, though the extent of information disclosure remains limited based on typical memory protection mechanisms.
From an operational perspective, this vulnerability represents a significant risk to MongoDB deployments where authenticated access exists, particularly in environments where database administrators or application users might have elevated privileges. The denial of service component creates immediate operational impact by potentially taking database services offline, affecting application availability and user access. Organizations running MongoDB instances must consider the potential for cascading effects if the database service becomes unavailable, especially in systems where multiple applications depend on MongoDB for core operations. The vulnerability demonstrates how seemingly innocuous parameter handling within aggregation pipelines can create substantial security risks.
Mitigation strategies should begin with immediate patching of affected MongoDB versions to address the out-of-bounds memory read issue, following vendor security advisories and release notes. Network segmentation and access controls should be implemented to limit authentication access to only necessary users and applications, reducing the attack surface for exploitation. Monitoring systems should be enhanced to detect unusual aggregation query patterns or repeated failed operations that might indicate attempted exploitation attempts. Additionally, implementing proper input validation and parameter sanitization within application code that interfaces with MongoDB can provide defense-in-depth measures. The vulnerability aligns with ATT&CK technique T1059.006: Command and Scripting Interpreter: Python within the context of database system manipulation, emphasizing the need for comprehensive security monitoring and access control measures to prevent unauthorized exploitation attempts.