CVE-2026-47276 in NanoMQ
Summary
by MITRE • 07/20/2026
In nanomq versions 0.24.11 and earlier, a NULL pointer dereference in `properties_parse()` allows an authenticated attacker to crash the NanoMQ broker by sending a POST request to `/api/v4/mqtt/publish` with `user_properties` as a JSON array instead of a JSON object. The crash occurs because `strlen()` is called on a NULL `item->string` pointer when iterating over array elements. An authenticated attacker can exploit this to crash the NanoMQ broker process. This is patched in version 0.24.14.
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Analysis
by VulDB Data Team • 07/20/2026
The vulnerability identified in nanomq versions 0.24.11 and earlier represents a critical NULL pointer dereference flaw within the MQTT broker's property parsing mechanism. This issue manifests specifically within the `properties_parse()` function where the application fails to properly validate input data structures before attempting to process them. The flaw occurs when an authenticated attacker submits a malicious POST request to the `/api/v4/mqtt/publish` endpoint with malformed user properties that are structured as a JSON array rather than the expected JSON object format.
The technical execution of this vulnerability relies on improper input validation within the MQTT broker's API handling layer. When the system processes the malformed user_properties field, it attempts to iterate through array elements expecting each item to contain a valid string pointer. However, during this iteration process, the code calls `strlen()` on what it believes to be a valid string pointer but which is actually NULL, causing an immediate segmentation fault and broker crash. This represents a classic CWE-476 NULL Pointer Dereference vulnerability that directly maps to the ATT&CK technique T1499.002 for network denial of service through application crashes.
The operational impact of this vulnerability extends beyond simple service disruption as it provides authenticated attackers with a reliable method to cause persistent broker failures. Since the attack requires only authentication credentials, which are typically less restricted than other system access mechanisms, this vulnerability can be exploited by malicious users who have legitimate access to the broker's API. The crash affects the entire broker process, potentially leading to extended downtime and loss of message queuing capabilities for all connected clients. Organizations relying on nanomq for MQTT message routing may experience significant service degradation or complete broker unavailability during exploitation attempts.
Mitigation strategies for this vulnerability require immediate patching to version 0.24.14 where the input validation has been corrected to properly handle both array and object formats for user_properties. Additionally, system administrators should implement proper monitoring of broker processes to detect unauthorized restarts or crashes that may indicate exploitation attempts. Network-level controls can be deployed to monitor and restrict access to the vulnerable API endpoint until patches are fully deployed across all affected systems. The fix demonstrates proper defensive programming practices by ensuring all pointer dereferences are validated before use, preventing the NULL pointer dereference condition that enabled the crash. Organizations should also consider implementing automated vulnerability scanning processes to identify other potential instances of similar input validation flaws within their MQTT broker implementations and related messaging infrastructure components.