CVE-2026-111383 in Nezha
Summary
by MITRE • 10/16/2026
Nezha from 2.0.13 before 2.3.15 contains a resource exhaustion vulnerability that allows authenticated users to open unbounded concurrent connections to the /api/v1/ws/transfer WebSocket endpoint. Attackers can hold thousands of subscriptions created by ServerTransferClass.Subscribe without limits, exhausting file descriptors, memory, and goroutines and blocking agent gRPC reconnections.
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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 located within the WebSocket handling logic for server transfer operations. Specifically, the /api/v1/ws/transfer endpoint fails to enforce limits on concurrent connections or subscriptions initiated by authenticated users. This architectural oversight allows an attacker who has obtained valid credentials to open an unbounded number of simultaneous WebSocket sessions. The core technical failure lies in the ServerTransferClass.Subscribe method, which does not implement any mechanism to cap the number of active subscriptions per user session or across the entire system. Consequently, a malicious actor can programmatically generate thousands of these subscriptions, each consuming significant backend resources including file descriptors, memory allocation for buffer management, and Go runtime goroutines dedicated to handling the persistent connection state.
From an operational perspective, this lack of rate limiting and concurrency control leads directly to service degradation and potential denial of service conditions. As the number of open connections escalates, the server's capacity to manage existing traffic diminishes rapidly due to resource saturation. The exhaustion of file descriptors prevents new network operations from being established, while memory pressure can lead to application crashes or instability within the Go runtime environment. A particularly severe consequence noted in reports is the blocking of agent gRPC reconnections. Since Nezha relies on these connections for monitoring and management tasks, an attacker exploiting this vulnerability effectively blinds the system by preventing legitimate agents from reconnecting, thereby disrupting administrative oversight and operational continuity even if the primary web interface remains partially accessible.
This flaw aligns with CWE-770: Allocation of Resources Without Limits or Throttling, as it involves failing to restrict resource consumption based on user input or session state. It also maps to MITRE ATT&CK technique T1499: Endpoint Denial of Service, specifically under the sub-category of Resource Exhaustion via Application Logic Flaws. The vulnerability is exploitable by authenticated users, which classifies it as an abuse of authentication mechanisms where valid credentials are leveraged for malicious resource consumption rather than unauthorized access to restricted data. This distinction highlights that even with proper identity verification in place, insufficient authorization checks regarding system resources can lead to significant security incidents.
To mitigate this vulnerability, immediate patching is required by upgrading Nezha to version 2.3.15 or later, where the developers have implemented necessary controls to limit concurrent connections and subscriptions. In environments where an upgrade cannot be performed immediately, network-level mitigations should be considered as a temporary countermeasure. Implementing rate limiting on the /api/v1/ws/transfer endpoint via reverse proxies such as Nginx can help restrict the number of WebSocket upgrades allowed per IP address or user token within a specific time window. Additionally, configuring connection timeouts and maximum concurrent session limits at the application configuration level may reduce the blast radius until the software is updated. Security teams should also monitor for unusual spikes in active WebSocket connections originating from single authenticated accounts to detect potential exploitation attempts early.