# CVE-2025-14847: The most severe memory leak vulnerability in MongoDB in years

## **Overview**

In recent years, MongoDB has often been considered a "secure by default" database management system if configured correctly. However, at the end of 2025, a serious vulnerability was discovered, challenging this assumption. **MongoBleed (CVE-2025-14847)** was discovered by chance and allows **remote attackers to directly read data in the memory (heap) of MongoDB without any form of authentication**, simply through specially crafted network packets.

The alarming aspect of MongoBleed is not the complexity of the exploit, but the **nature of the leaked data**. It's not logs or metadata, but **what MongoDB is "thinking" at that moment**: authentication information, BSON data not yet written to disk, session tokens, and other internal structures. This makes **MongoBleed** often compared to **Heartbleed**, one of the most shocking vulnerabilities in security history.

Immediately after the proof-of-concept was published, scanning and exploitation campaigns quickly appeared on the Internet, targeting tens of thousands of **publicly exposed MongoDB instances**. Let's explore how this vulnerability works, the level of risk if exploited, and how users can effectively protect themselves.

According to a report by **Censys,** more than 87,000 MongoDB instances have been affected by this vulnerability, with the majority located in the United States.

![Image from Censys showing MongoDB instances across the globe](https://www.tenable.com/sites/default/files/images/blog/90da7681-bdca-4f1e-ae9a-30a3f8a5eec6.png align="center")

## **Introduction to MongoDB**

**MongoDB** is a **NoSQL document-oriented database** management system designed to handle large volumes of data with high performance and flexible scalability. Instead of using the traditional table-row model like relational databases, MongoDB stores data as **BSON documents** (Binary JSON), allowing for the representation of complex, nested, and flexible data structures.

Architecturally, MongoDB is designed in a **client-server model,** where applications (clients) communicate directly with **mongod** through MongoDB's proprietary binary protocol (MongoDB Wire Protocol), by default on port **27017**.

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1767336033858/8a2fa276-3448-4a5f-99da-b573d0a0d72e.png align="center")

From a security perspective, MongoDB supports several defense mechanisms such as **user authentication, role-based access control (RBAC), TLS connection encryption, data-at-rest encryption, and audit logs**. However, in practice, many MongoDB systems are still **exposed directly to the Internet**, misconfigured, or slow to patch, making them attractive targets for attackers.

MongoDB uses the **Wire Protocol** to exchange messages between the client and server. A message typically includes:

* Header (opcode, requestId, responseTo)
    
* Payload (BSON documents, metadata)
    
* Compression options
    

To optimize performance and reduce bandwidth, MongoDB supports **Message Compression**, with **zlib** being the most common. When compression is enabled, data received from the client will be:

* Read into the network buffer
    
* Decompressed in memory
    
* Passed to the query processing layer
    

## **Cause of the Vulnerability**

As mentioned above in the architecture section of **MongoDB**, there is a part that supports **Message Compression, but this is also the security weakness leading to the CVE-2025-14847 vulnerability.** This feature allows any client, even those not authenticated, to trigger decompression logic and memory allocation. This results in a consequence:

* A portion of **uninitialized heap memory** is sent back to the client.
    
* The data leak is not due to "reading the wrong file," but due to **returning the wrong RAM.**
    

**CVE-2025-14847 exists not because MongoDB lacks security, but due to a wrong assumption at a very low level**:

* "Data after decompression is always safe to use."
    

## **Vulnerability Description**

* **Identifier:** CVE-2025-14847
    
* **CVSS Score:** 8.7
    
* **Severity Level:** High
    
* **Description:** Allows an unauthenticated attacker to extract sensitive data directly from the MongoDB server's memory remotely.
    

## **Affected Versions**

* 8.2.x < 8.2.3
    
* 8.0.x < 8.0.17
    
* 7.0.x < 7.0.28
    
* 6.0.x < 6.0.27
    
* 5.0.x < 5.0.32
    
* 4.4.x < 4.4.30
    

## **Setting Up the Environment**

To set up the environment, we can install it on both Windows and Ubuntu. In this example, we will set it up on Windows 10 with the following minimum requirements:

| Component | Recommended |
| --- | --- |
| OS | Windows 10 x64 |
| RAM | ≥ 4 GB |
| Disk | ≥ 5 GB free |
| System permissions | Administrator |
| Tool | PowerShell / CMD |

Visit MongoDB Community to download the installer: [https://www.mongodb.com/try/download/community](https://www.mongodb.com/try/download/community)

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1767340839540/366a1764-19b3-43aa-b6e6-a46db7b2c7cb.png align="center")

**Configuring MongoDB as a Service**

* `C:\Program Files\MongoDB\Server\8.2\data\`: Default Data Path
    
* `C:\Program Files\MongoDB\Server\8.2\log\`: Log Directory
    

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1767341441246/a4a7a4a1-1b3c-4e75-8c6d-f157f16bf2ba.png align="center")

**Connecting to MongoDB**

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1767343004757/e3ba6232-0356-4e26-97f7-73aaad928c61.png align="center")

## **Vulnerability Analysis and Demo**

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1767497681977/2bf5ad37-7125-4371-a364-5feda762e32d.png align="center")

As previously mentioned in the vulnerability cause and MongoDB's operation mechanism, the attacker will exploit the **protocol handling layer** of MongoDB, allowing an **unauthenticated client** to send syntactically valid requests that are specially crafted to:

* Trigger **unreleased memory allocation.**
    
* Gradually **increase the RAM usage of the mongod process.**
    
* Lead to **memory exhaustion** and denial of service.
    

In the first stage, the attacker will perform a network scan to find which host **has port 27017 open - this can also be considered a prerequisite for proceeding with the subsequent stages.**

After identifying the open port, the attacker continues to establish initial connections by having MongoDB accept connections at the **network layer and send some** protocol-compliant requests:

* Correct MongoDB Wire Protocol structure.
    
* No schema violations at the parser level.
    

With such valid requests, MongoDB receives and processes them as "normal" requests. During request processing, MongoDB will:

* Allocate buffer/object in the heap memory.
    
* Use it to process intermediate data.
    

After processing the requests, MongoDB will reach a stage called the **Memory Accumulation Phase. Here**, MongoDB **no longer processes queries at the application logic level but moves to internal memory handling (heap management). It will allocate temporary memory** to process valid network messages. Due to a logic error during processing, some memory is not reclaimed, leading to each processing cycle leaving behind a "residue" of memory—this is known as a **memory leak.**

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1767512728189/96453f58-6c2b-47d9-b39d-25092f0409ac.png align="center")

Not only does this vulnerability stop here, but if exploited, it also impacts the system.

**Short-term impact**

* RAM usage continuously increases
    
* Latency increases
    
* MongoDB responds slowly
    

**Long-term impact**

* OOM Killer (Linux)
    
* Service crash (Windows)
    
* Replica set:
    
    * Primary goes down
        
    * Trigger election
        
    * Causes cluster instability
        

In a production environment, this is an **infrastructure-level DoS**, not just an application error.

## **Conclusion**

The **MongoBleed (CVE-2025-14847)** exploitation campaign reveals a concerning reality: even popular, mature, and widely deployed database management systems like **MongoDB** can become serious vulnerabilities when there are errors in the **core memory processing layer**. Unlike traditional vulnerabilities that rely on authentication or authorization, MongoBleed allows attackers to **deplete server memory without authentication**, leading to denial of service, system disruption, and potential leakage of sensitive data.

The danger of this vulnerability lies in its ability to **directly exploit the protocol and internal memory management mechanisms**, completely bypassing typical security layers like user accounts, passwords, or role-based access control. In real-world environments, where many MongoDB instances are still exposed to the Internet or operate with default configurations, MongoBleed can become an effective attack tool for both **sabotage scenarios (DoS)** and **reconnaissance and preparation for deeper intrusions**.

Ultimately, MongoBleed is not just a single vulnerability, but also reflects a trend of attacks increasingly focusing on **foundational infrastructure components**. For security teams, understanding the internal workings of the system—from protocols and memory to actual deployment—is key to **early detection, effective response, and prevention of similar attack campaigns in the future**.

## **Recommendations**

1. **Patch and Upgrade (Highest Priority)**
    
    * **Upgrade MongoDB to the version that addresses CVE-2025-14847** as per MongoDB's official recommendations.
        
    * [Release Notes - Database Manual - MongoDB Docs](https://www.mongodb.com/docs/manual/release-notes/)
        
2. **Do Not Expose MongoDB Directly to the Internet**
    
    * **Absolutely do not expose port 27017** to the public Internet.
        
    * Allow MongoDB access only through:
        
        * Internal network (LAN/VPC)
            
        * VPN
            
        * Bastion host
            
    * Use a **firewall or security group** to restrict source IPs that are allowed to connect.
        
3. **Monitor memory resources and unusual behavior**
    
    * Set up alerts when:
        
        * Memory usage increases unexpectedly
            
        * MongoDB process continuously uses RAM without decreasing
            
    * Track metrics:
        
        * Resident Memory
            
        * WiredTiger cache usage
            
        * Unusual number of connections and requests
            
    * In a SOC environment, build a **normal behavior baseline** to detect early signs similar to MongoBleed.
        
4. **Limit resources to reduce attack impact**
    
    * Apply **resource limits**:
        
        * Limit RAM for MongoDB (especially in containers or VMs)
            
        * Limit the number of concurrent connections
            
    * In cloud or container environments:
        
        * Use cgroups / container memory limits
            
        * Avoid letting MongoDB consume all system RAM during an attack
            

## **Mapping MongoBleed using MITRE ATT&CK & D3FEND**

Phase 1 – Reconnaissance (Target Discovery)

* **T1046 – Network Service Discovery**
    
    * Attackers scan the network to find MongoDB with port 27017 open
        

**Phase 2 – Initial Access (Service Interaction)**

* **T1190 – Exploit Public-Facing Application**
    
    * MongoDB is considered a public-facing service
        
    * MongoDB protocol is exploited before authentication
        

**Phase 3 – Execution (Abuse of Server-Side Processing)**

* **T1059 (Conceptual)** – Command Execution (logic-level, not OS command)
    
* **T1106 – Native API Abuse** *(concept applied)*
    

**Phase 4 – Impact (Primary Objective)**

* **T1499.003 – Endpoint Denial of Service: Resource Exhaustion**
    
    * Exhaust RAM through memory leak
        

## **Reference**

1. [MongoBleed CVE-2025-14847 exploited in the wild | Tenable®](https://www.tenable.com/blog/cve-2025-14847-mongobleed-mongodb-memory-leak-vulnerability-exploited-in-the-wild)
    
2. [GitHub - joe-desimone/mongobleed](https://github.com/joe-desimone/mongobleed)
    
3. [MongoBleed (CVE-2025-14847): Risk, Detection & How Varonis Protects You](https://www.varonis.com/blog/mongobleed-cve-2025-14847-memory-leak-vulnerability)