CVE-2026-82066 Overview
CVE-2026-82066 is a heap out-of-bounds read vulnerability in the query planning component of MongoDB Server. An authenticated user with database read and write privileges can trigger the issue by submitting crafted query operations. The server then reads memory beyond allocated buffer boundaries. Revealed memory contents may be partially observable through diagnostic query statistics output. The weakness is categorized as [CWE-125] Out-of-bounds Read. Exploitation requires network access and low-privilege authentication but no user interaction.
Critical Impact
Authenticated attackers can trigger memory disclosure through crafted queries, potentially exposing sensitive server memory contents via query statistics output.
Affected Products
- MongoDB Server (query planning component)
- Refer to MongoDB Jira Issue SERVER-131562 for version-specific details
- Deployments exposing diagnostic query statistics to low-privilege users
Discovery Timeline
- 2026-09-08 - CVE CVE-2026-82066 published to NVD
- 2026-09-08 - Last updated in NVD database
Technical Details for CVE-2026-82066
Vulnerability Analysis
The vulnerability resides in the query planner subsystem of MongoDB Server. When processing crafted query operations, the planner reads memory outside the bounds of allocated heap buffers. The out-of-bounds bytes are not fully filtered before being incorporated into diagnostic outputs. As a result, portions of adjacent heap memory can surface in query statistics visible to the requesting user. This creates a confidentiality issue rather than a code execution or integrity risk.
Exploitation requires an account with read and write privileges on a database. No user interaction is needed, and the attack is executed over the network against the MongoDB service. The vulnerability does not affect service availability or data integrity, based on the published impact metrics.
Root Cause
The root cause is missing or insufficient bounds validation in the query planning code path. The planner dereferences buffer offsets derived from attacker-controlled query structure without verifying that offsets remain within allocated boundaries. This behavior matches the pattern described in [CWE-125] Out-of-bounds Read, where a product reads data past the end of the intended buffer.
Attack Vector
An authenticated database user submits specially crafted query operations to the MongoDB Server. The planner processes these operations and reads adjacent heap memory during plan construction or evaluation. The attacker then invokes diagnostic query statistics functionality to retrieve output that partially reflects the disclosed memory. Repeated invocation with varying query shapes can incrementally expose additional memory regions.
No verified exploit code or public proof of concept is available at publication. See the MongoDB Jira Issue SERVER-131562 advisory for authoritative technical details.
Detection Methods for CVE-2026-82066
Indicators of Compromise
- Unusual volumes of query statistics or explain-plan requests from a single authenticated principal
- Repeated queries with unusual or malformed query predicates against multiple collections
- Query statistics output containing non-printable byte sequences or values inconsistent with schema
Detection Strategies
- Enable MongoDB audit logging for authenticated query operations and diagnostic commands
- Alert on accounts that issue high-volume diagnostic queries relative to baseline behavior
- Correlate query planner errors and warnings in server logs with the originating client identity
Monitoring Recommendations
- Monitor authentication events for low-privilege accounts accessing production databases
- Track outbound network flows from MongoDB instances for anomalous data volumes
- Review role assignments to confirm the principle of least privilege for read/write users
How to Mitigate CVE-2026-82066
Immediate Actions Required
- Apply the vendor-supplied patch referenced in MongoDB Jira Issue SERVER-131562 once available for your release
- Audit database roles and revoke read/write privileges from accounts that do not require them
- Restrict access to diagnostic query statistics commands to trusted operational accounts
Patch Information
MongoDB tracks the fix in SERVER-131562. Consult the linked issue for fixed versions and backport availability across supported release lines. Apply the corresponding upgrade to all affected replica set members and sharded cluster components.
Workarounds
- Limit network exposure of MongoDB endpoints to trusted application tiers using firewall rules
- Disable or restrict diagnostic query statistics output for non-administrative roles where feasible
- Enforce strong role-based access control to minimize the population of users who meet the exploit precondition
# Example: revoke readWrite from a non-essential user in the mongo shell
use admin
db.revokeRolesFromUser("reporting_user", [ { role: "readWrite", db: "production" } ])
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
