CVE-2025-6714: MongoDB Server DoS Vulnerability

CVE-2025-6714 Overview

MongoDB Server's mongos component can become unresponsive to new connections due to incorrect handling of incomplete data. This vulnerability affects MongoDB when configured with load balancer support in sharded cluster deployments using HAProxy on specified ports. The flaw allows attackers to exhaust server resources by sending malformed or incomplete requests, effectively causing a denial of service condition.

Critical Impact

Network-accessible attackers can render MongoDB sharded clusters unresponsive by exploiting improper data handling in the mongos routing component, disrupting database availability for all connected applications.

Affected Products

• MongoDB Server v6.0 prior to 6.0.23
• MongoDB Server v7.0 prior to 7.0.20
• MongoDB Server v8.0 prior to 8.0.9

Discovery Timeline

• 2025-07-07 - CVE CVE-2025-6714 published to NVD
• 2025-10-03 - Last updated in NVD database

Technical Details for CVE-2025-6714

Vulnerability Analysis

This vulnerability (classified as CWE-400: Uncontrolled Resource Consumption) exists in the mongos query router component of MongoDB sharded clusters. When load balancer support is enabled—typically through HAProxy integration—the mongos process incorrectly handles incomplete or malformed data streams from client connections.

The vulnerability specifically impacts environments where MongoDB sharded clusters are deployed behind a load balancer. In this configuration, the mongos component fails to properly timeout or terminate connections that send partial data, causing connection handlers to remain in a waiting state indefinitely. As these stalled connections accumulate, the mongos process exhausts its connection pool and available resources, eventually becoming unresponsive to legitimate new connection requests.

The attack can be executed remotely without authentication and requires no user interaction, making it particularly dangerous for internet-facing MongoDB deployments. Organizations using HAProxy or similar load balancers in front of their MongoDB sharded clusters are at elevated risk.

Root Cause

The root cause stems from improper input validation and resource management in the mongos component's connection handling logic. When operating behind a load balancer, the mongos process does not adequately enforce timeouts or resource limits on connections that transmit incomplete data packets. This allows malicious or malfunctioning clients to hold connections open indefinitely, consuming server resources without completing valid operations.

Attack Vector

The attack exploits the network-accessible mongos service by establishing connections through the load balancer and intentionally sending incomplete data. The attacker does not need valid credentials or specific privileges to exploit this vulnerability. By opening multiple connections and leaving data transmissions incomplete, an attacker can systematically exhaust the connection pool, causing the mongos instance to stop accepting new connections from legitimate clients.

The vulnerability requires the target MongoDB deployment to be configured with load balancer support for mongos using HAProxy. Without this specific configuration, the vulnerability is not exploitable.

Detection Methods for CVE-2025-6714

Indicators of Compromise

• Unusual increase in stalled or long-lived connections to mongos instances
• Connection pool exhaustion events in MongoDB logs
• Sudden inability for applications to establish new connections to the sharded cluster
• HAProxy health check failures for mongos backend servers
• Elevated memory consumption on mongos processes without corresponding query activity

Detection Strategies

• Monitor MongoDB connection metrics using db.serverStatus().connections for abnormal patterns in current and available connections
• Configure alerting for mongos connection pool exhaustion thresholds
• Implement network-level monitoring to detect connection flooding patterns targeting MongoDB ports
• Review MongoDB logs for connection timeout and resource exhaustion warnings
• Deploy SentinelOne Singularity to detect anomalous process behavior and resource consumption patterns

Monitoring Recommendations

• Enable verbose logging on mongos instances to capture connection lifecycle events
• Configure HAProxy to log detailed connection statistics and timeout events
• Set up automated alerting when mongos connection counts approach configured limits
• Implement regular health checks that verify new connections can be established successfully

How to Mitigate CVE-2025-6714

Immediate Actions Required

• Upgrade MongoDB Server v6.0 to version 6.0.23 or later
• Upgrade MongoDB Server v7.0 to version 7.0.20 or later
• Upgrade MongoDB Server v8.0 to version 8.0.9 or later
• Review HAProxy configurations for appropriate connection and timeout limits
• Consider temporarily disabling load balancer support if not critical to operations

Patch Information

MongoDB has released security patches addressing this vulnerability. Refer to MongoDB Jira Issue SERVER-106753 for detailed information about the fix and release notes for the patched versions. Organizations should prioritize upgrading to the fixed versions: 6.0.23, 7.0.20, or 8.0.9 depending on their deployed major version.

Workarounds

• Implement strict connection timeouts at the HAProxy layer to terminate incomplete connections
• Configure rate limiting on the load balancer to prevent connection flooding
• Restrict network access to mongos instances using firewall rules or security groups
• Deploy additional mongos instances to increase overall connection capacity and resilience
• Monitor and alert on connection metrics to enable rapid response to exploitation attempts

# HAProxy configuration example for connection timeout protection
# Add to your HAProxy frontend or backend configuration for mongos
frontend mongodb_frontend
    bind *:27017
    mode tcp
    timeout client 30s
    timeout connect 10s
    default_backend mongos_servers

backend mongos_servers
    mode tcp
    timeout server 30s
    timeout check 5s
    server mongos1 192.168.1.10:27017 check inter 5s fall 3