CVE-2026-18888: MongoDB BI Connector Buffer Overflow Flaw

CVE-2026-18888 Overview

The MongoDB Business Intelligence (BI) Connector Open Database Connectivity (ODBC) Driver contains an out-of-bounds write vulnerability [CWE-787] when converting floating point column values into text representation. The driver fails to validate that the converted text fits within the destination buffer before writing. An authenticated user who can insert data into a collection exposed through the BI Connector can trigger memory corruption in a downstream reading application. The result is application crashes and potential adjacent memory corruption when the reader processes sufficiently large floating point values.

Critical Impact
A low-privileged user with write access to a MongoDB collection can crash any application that reads floating point data through the BI Connector ODBC Driver, disrupting analytics and reporting workflows.

Affected Products

MongoDB BI Connector ODBC Driver versions prior to v1.4.9
Applications using the MongoDB BI Connector for SQL-based analytics access
Business intelligence and reporting tools relying on the affected ODBC driver

Discovery Timeline

2026-08-12 - CVE-2026-18888 published to the National Vulnerability Database (NVD)
2026-08-12 - Last updated in NVD database
Patch Release - MongoDB published fixed version v1.4.9 on GitHub

Technical Details for CVE-2026-18888

Vulnerability Analysis

The vulnerability resides in the floating point to text conversion routine within the MongoDB BI Connector ODBC Driver. The driver serializes numeric column values retrieved from MongoDB into their textual representation to satisfy ODBC client requests. During this conversion, the driver does not verify that the resulting string length fits within the caller-supplied destination buffer.

When the textual form of a floating point number exceeds the buffer capacity, the driver writes past the buffer boundary. This out-of-bounds write corrupts adjacent memory regions in the client process. The corruption typically manifests as an application crash, producing a denial-of-service condition for analytics and reporting tools that depend on the driver.

Root Cause

The defect is a classic missing bounds check [CWE-787]. The conversion routine assumes a fixed maximum output length that does not account for the full range of representable double-precision floating point values, including denormalized numbers, scientific notation edge cases, and precision expansion during formatting.

Attack Vector

An attacker requires low privileges: the ability to write a single floating point value into a MongoDB collection that is exposed via the BI Connector. When any downstream application subsequently reads that collection through the ODBC driver, the malformed value triggers the out-of-bounds write. No user interaction on the victim side is required beyond the routine data read.

Exploitation code is not required for impact. See the MongoDB BI Connector ODBC Driver v1.4.9 release for the patched conversion logic.

Detection Methods for CVE-2026-18888

Indicators of Compromise

Unexpected crashes or access violations in BI tools, reporting engines, or custom applications using the MongoDB BI Connector ODBC Driver
Process termination logs referencing the MongoDB ODBC driver module during read operations against MongoDB collections
MongoDB audit log entries showing writes of unusually large or precision-extreme floating point values by low-privileged accounts

Detection Strategies

Inventory all hosts running the MongoDB BI Connector ODBC Driver and identify installed versions to flag installations older than v1.4.9
Monitor MongoDB collections exposed through the BI Connector for insertions of floating point values with extreme magnitudes or precision
Correlate ODBC client process crashes with recent MongoDB write activity to identify potential trigger events

Monitoring Recommendations

Enable MongoDB auditing on collections accessible through the BI Connector to capture write operations and originating accounts
Collect Windows Error Reporting or crash dumps from BI reporting servers to identify recurring faults in the ODBC driver
Alert on repeated abnormal terminations of the same reporting process within short time windows

How to Mitigate CVE-2026-18888

Immediate Actions Required

Upgrade the MongoDB BI Connector ODBC Driver to version v1.4.9 or later on all systems that connect to MongoDB via the BI Connector
Audit MongoDB role assignments to ensure only trusted accounts hold write privileges on collections exposed through the BI Connector
Review recent write activity on affected collections for anomalous floating point values that may indicate prior exploitation attempts

Patch Information

MongoDB released the fix in the MongoDB BI Connector ODBC Driver v1.4.9 release. The patched version validates the destination buffer size before writing the converted floating point text, preventing the out-of-bounds write condition.

Workarounds

Restrict write access to MongoDB collections accessed through the BI Connector to trusted service accounts only
Apply schema validation rules on affected collections to reject floating point values outside expected numeric ranges
Isolate BI reporting workloads on dedicated hosts to contain the impact of driver crashes on other services

bash

# Verify the installed MongoDB BI Connector ODBC Driver version on Windows
reg query "HKLM\SOFTWARE\ODBC\ODBCINST.INI\MongoDB ODBC ANSI Driver" /v DriverVersion

# On Linux, inspect the installed driver package version
dpkg -l | grep -i mongodb-odbc
rpm -qa | grep -i mongodb-odbc