CVE-2026-111384 in Nezha
Summary
by MITRE • 10/16/2026
Nezha 1.0.0 before 2.3.15 contains a memory exhaustion vulnerability in the dashboard file manager WebSocket endpoint because fmStream never calls SetReadLimit, leaving message size unbounded. Authenticated users with file manager scopes can send one oversized binary message to /api/v1/ws/file/:id, triggering an OOM kill that drops all agent monitoring.
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Analysis
by VulDB Data Team • 10/16/2026
The vulnerability identified in Nezha versions prior to 2.3.15 represents a critical resource exhaustion flaw within the dashboard's file management subsystem. Specifically, this issue resides in the WebSocket endpoint responsible for handling file stream operations, located at the path /api/v1/ws/file/:id. The root cause of this defect is a failure to implement proper message size constraints on incoming data streams. In Go-based applications utilizing the gorilla/websocket or similar libraries, it is standard practice to call SetReadLimit on websocket connections to restrict the maximum allowed frame size for read operations. By omitting this crucial configuration step in the fmStream handler, the application leaves the message size completely unbounded and unrestricted by any predefined threshold.
This architectural oversight allows an authenticated user possessing file manager scopes to exploit the system through a straightforward mechanism. The attacker can establish a connection to the vulnerable WebSocket endpoint and transmit a single binary message of excessive volume. Because there is no limit imposed on the amount of data that can be read into memory at once, the application attempts to allocate sufficient heap space to accommodate this oversized payload in its entirety before processing it further. This sudden spike in memory consumption rapidly depletes available system resources, leading directly to an Out Of Memory condition.
The operational impact of this vulnerability is severe and disruptive to service availability. When the server encounters a fatal out-of-memory error, the operating system's kernel typically intervenes by invoking the OOM killer process. This mechanism forcibly terminates the most memory-intensive processes on the host machine, which in this context includes the Nezha agent monitoring services running alongside or dependent on the dashboard infrastructure. Consequently, all active agent monitoring is abruptly dropped, resulting in a complete loss of visibility into server health and status metrics for administrators. This constitutes a significant denial-of-service scenario that can be triggered remotely by any authenticated user with specific file management permissions.
From a classification perspective, this vulnerability aligns closely with CWE-400, which describes uncontrolled resource consumption leading to exhaustion conditions. It also relates to CWE-789, as the lack of input validation regarding data size allows for memory corruption or excessive allocation that destabilizes the application environment. In terms of offensive security frameworks such as MITRE ATT&CK, this behavior is consistent with techniques involving Denial of Service via resource consumption, where an adversary leverages valid credentials to degrade service availability rather than compromising confidentiality or integrity directly.
To mitigate this risk, immediate remediation requires upgrading Nezha to version 2.3.15 or later, which includes the necessary code fixes to enforce message size limits on WebSocket connections. For environments that cannot immediately upgrade, a temporary workaround involves restricting access to the /api/v1/ws/file/:id endpoint through network-level controls such as firewalls or reverse proxy configurations, ensuring that only trusted internal networks can reach this specific service path. Additionally, implementing strict rate limiting and connection quotas at the load balancer level can help dampen the impact of any potential exploitation attempts by capping the volume of data transmitted over WebSocket connections before it reaches the vulnerable application layer.