CVE-2026-13066: MongoDB Information Disclosure Vulnerability

CVE-2026-13066 Overview

CVE-2026-13066 is an information disclosure vulnerability in MongoDB's server-side JavaScript engine. The flaw stems from improper handling of DBPointer objects during Binary JSON (BSON) serialization. When affected code paths process these objects, uninitialized regions of process memory can be included in responses returned to the client.

The vulnerability requires low-privileged network access and impacts deployments that enable server-side JavaScript execution. Authenticated attackers can trigger the flaw to leak fragments of MongoDB process memory, which may contain sensitive data such as query results, credentials, or cryptographic material handled by adjacent operations.

Critical Impact
Authenticated attackers can retrieve fragments of MongoDB internal process memory through crafted BSON documents containing DBPointer objects, exposing sensitive data handled by the database process.

Affected Products

MongoDB Server deployments with server-side JavaScript enabled
MongoDB configurations invoking DBPointer object serialization through the JavaScript engine
See MongoDB Jira ticket SERVER-127694 for version-specific fix information

Discovery Timeline

2026-07-22 - CVE-2026-13066 published to NVD
2026-07-22 - Last updated in NVD database

Technical Details for CVE-2026-13066

Vulnerability Analysis

The vulnerability resides in the BSON serialization path used by MongoDB's server-side JavaScript engine. BSON is the binary-encoded document format MongoDB uses for storage and network transport. When the serializer encounters a DBPointer type, it fails to correctly initialize or bound the memory region copied into the outbound BSON document.

As a result, bytes from the MongoDB server process address space adjacent to the intended payload are included in the response. This behavior maps to [CWE-843] (Access of Resource Using Incompatible Type), reflecting a type confusion condition during serialization of the deprecated DBPointer BSON type.

Root Cause

The root cause is improper handling of DBPointer objects inside the JavaScript engine's BSON encoder. The encoder treats the object's underlying buffer without validating length or initializing the destination correctly. Memory contents that were never intended for the client are serialized alongside legitimate document fields.

Attack Vector

An authenticated attacker with permissions to execute server-side JavaScript submits a query, aggregation stage, or map-reduce operation that constructs or references a DBPointer value. The server serializes the result and returns memory contents to the attacker. Repeated invocations can be used to sample different regions of process memory over time.

The attack requires network access to the MongoDB service and valid credentials with sufficient privileges to run server-side JavaScript. No user interaction is needed. See the MongoDB advisory in SERVER-127694 for technical details.

Detection Methods for CVE-2026-13066

Indicators of Compromise

Query, aggregation, or map-reduce operations that construct or reference DBPointer BSON types from server-side JavaScript contexts
Repeated small-result queries from a single authenticated identity targeting $where, mapReduce, or $function operators
Client responses containing high-entropy binary payloads inconsistent with expected document schemas

Detection Strategies

Enable MongoDB audit logging and alert on invocations of server-side JavaScript operators, especially from non-administrative accounts
Baseline normal application query patterns and flag deviations that include DBPointer type references or unusual BSON element types
Correlate application-tier and database-tier logs to identify queries that originate outside expected application code paths

Monitoring Recommendations

Track authentication events for accounts granted the javascript privilege or roles capable of executing server-side JavaScript
Monitor MongoDB response sizes for statistical anomalies that may indicate memory oversharing
Forward MongoDB audit logs to a centralized analytics platform to enable retroactive hunting for DBPointer misuse

How to Mitigate CVE-2026-13066

Immediate Actions Required

Disable server-side JavaScript execution unless required by application workloads by setting security.javascriptEnabled to false
Inventory all MongoDB deployments and identify clusters where server-side JavaScript is enabled
Rotate credentials and secrets that may have been present in MongoDB process memory during the exposure window
Review MongoDB role assignments and revoke server-side JavaScript privileges from accounts that do not require them

Patch Information

MongoDB has tracked remediation under Jira ticket SERVER-127694. Administrators should consult the MongoDB security advisories page for the fixed version corresponding to their release branch and upgrade affected deployments.

Workarounds

Set security.javascriptEnabled: false in mongod.conf to disable server-side JavaScript across the cluster
Restrict use of $where, mapReduce, $function, and $accumulator operators through role-based access control
Place MongoDB instances behind network segmentation so that only trusted application tiers can reach the database port
Apply the least-privilege principle to database users and remove the built-in javascript privilege from non-essential roles

bash

# Configuration example: disable server-side JavaScript in mongod.conf
security:
  javascriptEnabled: false

# Verify the setting at runtime
mongosh --eval "db.adminCommand({ getParameter: 1, javascriptEnabled: 1 })"