CVE-2026-6914: MongoDB Server DoS Vulnerability

CVE-2026-6914 Overview

CVE-2026-6914 is an Integer Underflow vulnerability (CWE-191) in MongoDB Server that can cause a Denial of Service condition. Computing the MD5 checksum of a malformed BSON object under specific conditions may cause loss of availability in the MongoDB server. This vulnerability allows authenticated attackers with network access to disrupt database operations by sending specially crafted BSON objects.

Critical Impact

Authenticated attackers can exploit this vulnerability to cause complete loss of availability of MongoDB database servers, potentially disrupting critical applications and services relying on the affected database infrastructure.

Affected Products

• MongoDB Server v8.2 (all versions)
• MongoDB Server v8.1 (all versions)
• MongoDB Server v8.0 versions prior to 8.0.21
• MongoDB Server v7.0 versions prior to 7.0.32

Discovery Timeline

• 2026-04-29 - CVE CVE-2026-6914 published to NVD
• 2026-04-29 - Last updated in NVD database

Technical Details for CVE-2026-6914

Vulnerability Analysis

This vulnerability stems from an integer underflow condition (CWE-191) that occurs when MongoDB Server processes malformed BSON (Binary JSON) objects during MD5 checksum computation. When a specially crafted BSON document is submitted to the server, the checksum calculation routine may encounter unexpected size values that trigger an integer underflow, leading to memory access violations or infinite loops that result in server unavailability.

The vulnerability requires low privileges to exploit, meaning an authenticated user with basic database access can trigger the condition. While the vulnerability does not allow for data confidentiality or integrity breaches, the availability impact is significant as it can render the entire MongoDB instance unresponsive.

Root Cause

The root cause is an integer underflow vulnerability (CWE-191) in the BSON document processing logic. When computing MD5 checksums, the server fails to properly validate BSON object size fields before performing arithmetic operations. Malformed BSON objects with manipulated size values can cause unsigned integer arithmetic to underflow, resulting in unexpected large values that corrupt memory calculations or cause resource exhaustion loops.

Attack Vector

The attack is network-based and requires low-privilege authentication to the MongoDB server. An attacker must be able to submit BSON documents to the database, which is a common operation available to most authenticated users. The attacker crafts a malformed BSON object with specific field manipulations that trigger the integer underflow during MD5 checksum computation.

The vulnerability is triggered when the server attempts to compute an MD5 checksum of the malformed BSON document. This can occur through various database operations including document insertion, aggregation pipelines, or other operations that invoke checksum validation. No user interaction is required beyond the initial authentication.

For technical details on the specific conditions that trigger this vulnerability, refer to the MongoDB Jira Ticket SERVER-119981.

Detection Methods for CVE-2026-6914

Indicators of Compromise

• Unexpected MongoDB server crashes or restarts with memory-related errors in logs
• Database connection timeouts or unresponsive MongoDB instances following document operations
• Log entries indicating BSON parsing errors or checksum computation failures
• Unusual patterns of authenticated connections submitting malformed documents

Detection Strategies

• Monitor MongoDB server logs for BSON parsing errors and checksum-related exceptions
• Implement alerting on sudden MongoDB service availability drops or restart patterns
• Deploy network-level monitoring to detect anomalous BSON document sizes in MongoDB protocol traffic
• Review authentication logs for accounts submitting documents immediately before server instability

Monitoring Recommendations

• Configure MongoDB profiling to capture operations that precede server instability events
• Set up real-time alerting for MongoDB process terminations and memory allocation failures
• Monitor system metrics for sudden CPU spikes or memory exhaustion on MongoDB hosts
• Implement application-level health checks that can detect MongoDB unavailability

How to Mitigate CVE-2026-6914

Immediate Actions Required

• Upgrade MongoDB Server v8.0 to version 8.0.21 or later immediately
• Upgrade MongoDB Server v7.0 to version 7.0.32 or later immediately
• For MongoDB Server v8.1 and v8.2, consult MongoDB vendor channels for available patches
• Review and restrict database user permissions to minimize attack surface from authenticated users

Patch Information

MongoDB has released patched versions to address this vulnerability:

• MongoDB Server 8.0: Upgrade to version 8.0.21 or later
• MongoDB Server 7.0: Upgrade to version 7.0.32 or later

For MongoDB Server versions 8.1 and 8.2, all versions are affected. Administrators should monitor the MongoDB Jira Ticket SERVER-119981 for patch availability announcements and consult MongoDB support for guidance on remediation options.

Workarounds

• Implement strict input validation at the application layer before documents reach MongoDB
• Restrict MongoDB network access to trusted application servers using firewall rules
• Apply the principle of least privilege to database user accounts to limit potential attackers
• Consider deploying MongoDB replica sets to maintain availability during potential exploitation attempts

# Configuration example
# Restrict MongoDB to listen only on trusted interfaces
# Edit /etc/mongod.conf
net:
  bindIp: 127.0.0.1,192.168.1.100  # Only bind to localhost and trusted internal IP
  port: 27017

# Enable authentication if not already enabled
security:
  authorization: enabled

# Restart MongoDB after configuration changes
# systemctl restart mongod