CVE-2026-25611: MongoDB Server DOS Vulnerability

CVE-2026-25611 Overview

A memory exhaustion vulnerability exists in MongoDB Server that allows unauthenticated remote attackers to crash database servers by sending specially crafted messages. This denial of service condition results from improper handling of asymmetric resource consumption, where malicious network requests can consume excessive memory resources without proper validation or limits.

Critical Impact

Unauthenticated attackers can remotely crash MongoDB servers through memory exhaustion, causing service disruption and potential data availability issues for dependent applications.

Affected Products

• MongoDB Server (specific versions to be confirmed via vendor advisories)

Discovery Timeline

• 2026-02-10 - CVE-2026-25611 published to NVD
• 2026-02-10 - Last updated in NVD database

Technical Details for CVE-2026-25611

Vulnerability Analysis

This vulnerability falls under CWE-405 (Asymmetric Resource Consumption), a class of denial of service vulnerabilities where an attacker can cause disproportionate resource consumption with minimal effort. In this case, specifically crafted network messages trigger excessive memory allocation on the MongoDB server without requiring authentication.

The attack exploits the message handling mechanism in MongoDB's network protocol layer. When the server receives these malformed messages, it allocates memory to process them but fails to implement adequate bounds checking or resource limits. This allows an attacker to rapidly exhaust available server memory through a series of lightweight requests, ultimately causing the MongoDB process to crash due to out-of-memory conditions.

The vulnerability is particularly concerning because it requires no authentication, meaning any network-accessible MongoDB instance is potentially at risk. Organizations exposing MongoDB servers to untrusted networks or the internet face elevated risk of exploitation.

Root Cause

The root cause stems from improper resource management in MongoDB's message parsing and processing code. The server fails to enforce appropriate limits on memory allocation when handling certain message types, allowing unbounded memory growth. This represents a classic asymmetric resource consumption pattern where the computational cost for an attacker is trivial compared to the resources consumed on the target system.

Attack Vector

The attack is conducted over the network and requires no authentication or user interaction. An attacker with network access to the MongoDB server port (default 27017) can send a series of maliciously crafted messages that trigger the memory exhaustion condition. The attack does not require special privileges or valid database credentials, making it accessible to any attacker who can reach the MongoDB service.

The exploitation pattern involves sending multiple crafted messages in sequence, each causing the server to allocate memory that is not properly reclaimed. As memory consumption grows, system performance degrades until the MongoDB process is terminated by the operating system's out-of-memory killer or crashes due to allocation failures.

Detection Methods for CVE-2026-25611

Indicators of Compromise

• Unusual memory consumption patterns on MongoDB server processes
• MongoDB server crashes with out-of-memory errors in system logs
• High volume of malformed or unusual connection attempts to MongoDB ports
• Repeated MongoDB service restarts without clear operational cause

Detection Strategies

• Monitor MongoDB process memory usage for abnormal growth patterns
• Implement network traffic analysis to detect malformed MongoDB wire protocol messages
• Configure alerting on MongoDB crash events and unexpected service restarts
• Deploy intrusion detection rules to identify potential exploitation attempts targeting port 27017

Monitoring Recommendations

• Enable comprehensive MongoDB logging including connection events and error conditions
• Implement memory usage thresholds with automated alerts when consumption exceeds normal baselines
• Monitor network traffic patterns to MongoDB instances for anomalous connection rates
• Use application performance monitoring to track database availability and response times

How to Mitigate CVE-2026-25611

Immediate Actions Required

• Restrict network access to MongoDB servers using firewall rules to allow only trusted clients
• Enable MongoDB authentication if not already configured to add a defense layer
• Monitor MongoDB server memory consumption and configure automatic restart on failure
• Review MongoDB deployment architecture to ensure servers are not exposed to untrusted networks

Patch Information

MongoDB has tracked this issue across multiple JIRA tickets. Organizations should monitor these issues for patch availability and upgrade guidance:

• MongoDB Server Issue SERVER-116206
• MongoDB Server Issue SERVER-116210
• MongoDB Server Issue SERVER-116211

Consult MongoDB's official security advisories for specific patched versions and upgrade instructions.

Workarounds

• Implement network segmentation to isolate MongoDB servers from untrusted networks
• Configure operating system memory limits (cgroups on Linux) to prevent complete system resource exhaustion
• Deploy a reverse proxy or connection pooler with rate limiting capabilities in front of MongoDB
• Enable MongoDB's built-in connection limits using maxIncomingConnections configuration parameter

# Example: Configure connection limits in mongod.conf
net:
  maxIncomingConnections: 1000
  bindIp: 127.0.0.1,internal-network-ip

# Example: Linux cgroup memory limit for MongoDB process
systemctl set-property mongod.service MemoryMax=8G