Overview
A critical Heap-Use-After-Free (UAF) vulnerability, identified as CVE-2025-65953, has been discovered in the NanoMQ MQTT Broker (NanoMQ), an all-around Edge Messaging Platform. This vulnerability affects versions prior to 0.22.5. The root cause lies within the TCP transport component of NanoMQ, specifically interacting with the underlying NanoNNG library.
Technical Details
The vulnerability is located in src/sp/transport/mqtt/broker_tcp.c of the NanoNNG library. It stems from improper resource management and premature cleanup of message and pipe structures. This occurs under specific conditions involving malformed MQTTV5 retain message traffic.
Essentially, when NanoMQ processes certain types of malformed MQTTV5 retain messages, it may prematurely free memory associated with message or pipe structures. Subsequent attempts to access this freed memory can lead to a crash, denial-of-service, or potentially even arbitrary code execution.
CVSS Analysis
Due to the nature of the vulnerability, a successful exploit could lead to a denial-of-service condition, system instability, or potentially even remote code execution. However, the current CVSS score is marked as N/A. A thorough evaluation is underway to determine a definitive CVSS score reflecting the accurate severity.
Possible Impact
The impact of this vulnerability can be significant, especially in environments where NanoMQ is used in critical infrastructure or handles sensitive data. Potential consequences include:
- Denial of Service (DoS): An attacker could craft malicious MQTTV5 retain messages to trigger the UAF vulnerability, causing the NanoMQ broker to crash, thereby disrupting MQTT communication.
- System Instability: Repeated triggering of the vulnerability could lead to instability and unpredictable behavior of the host system.
- Potential Code Execution: While not confirmed, the UAF vulnerability *could* potentially be exploited to achieve arbitrary code execution, depending on memory layout and system configuration. This requires further investigation.
Mitigation or Patch Steps
The vulnerability has been patched in NanoMQ version 0.22.5. Users of NanoMQ are strongly advised to upgrade to version 0.22.5 or later as soon as possible.
To mitigate the risk before upgrading, consider implementing the following measures:
- Input Validation: Implement strict input validation on MQTT messages to filter out malformed or suspicious messages.
- Network Segmentation: Isolate the NanoMQ broker within a segmented network to limit the potential impact of a successful exploit.
- Rate Limiting: Implement rate limiting on MQTT message traffic to prevent an attacker from flooding the broker with malicious messages.
