CVE-2026-41400: OpenClaw WebSocket DoS Vulnerability

CVE-2026-41400 Overview

CVE-2026-41400 is a resource exhaustion vulnerability in OpenClaw's voice-call component that represents an incomplete fix for CVE-2026-32062. The vulnerability allows remote attackers to send oversized pre-start WebSocket frames to the voice-call media stream handler, causing excessive resource consumption and denial of service conditions.

Critical Impact
Remote attackers can exhaust server resources by sending oversized WebSocket frames before the start validation occurs, disrupting voice-call services for legitimate users.

Affected Products

OpenClaw versions before 2026.3.31
OpenClaw voice-call extension component
Systems utilizing OpenClaw WebSocket media streaming

Discovery Timeline

2026-04-28 - CVE-2026-41400 published to NVD
2026-04-28 - Last updated in NVD database

Technical Details for CVE-2026-41400

Vulnerability Analysis

This vulnerability stems from an incomplete patch for CVE-2026-32062, where the voice-call component fails to properly validate WebSocket frame sizes before the session start validation occurs. The media-stream.ts module in the voice-call extension processes incoming WebSocket frames without adequate size restrictions during the pre-start phase, allowing attackers to submit arbitrarily large frames that consume system memory and processing resources.

The flaw is classified under CWE-770 (Allocation of Resources Without Limits or Throttling), indicating that the application does not properly limit resource allocation when handling WebSocket data. This allows network-based attackers to exploit the vulnerability without authentication, though the direct impact is limited to service availability rather than data confidentiality or integrity.

Root Cause

The root cause lies in the order of operations within the WebSocket frame processing logic. The voice-call component parses and processes incoming WebSocket frames in their entirety before performing start validation checks. This means oversized frames are fully allocated in memory before any validation can reject them, creating a window for resource exhaustion attacks. The incomplete fix for CVE-2026-32062 addressed some validation scenarios but failed to account for pre-start frame handling.

Attack Vector

The attack vector is network-based, requiring no authentication or user interaction. An attacker can establish a WebSocket connection to the voice-call endpoint and send specially crafted oversized frames during the pre-start phase. Because frame size validation occurs after memory allocation, each malicious frame consumes resources before being rejected. By sending multiple oversized frames in rapid succession, an attacker can exhaust available server resources, causing denial of service for legitimate voice-call users.

typescript

 
import type { IncomingMessage } from "node:http";
import type { Duplex } from "node:stream";
-import { WebSocket, WebSocketServer } from "ws";
+import { type RawData, WebSocket, WebSocketServer } from "ws";
import type {
  OpenAIRealtimeSTTProvider,
  RealtimeSTTSession,

Source: GitHub Commit Update

Detection Methods for CVE-2026-41400

Indicators of Compromise

Abnormally large WebSocket frames (exceeding normal voice-call frame sizes) directed at the voice-call endpoint
Spike in memory consumption on servers running the OpenClaw voice-call component
Connection patterns showing rapid WebSocket connections with large payloads but no successful session starts
Server logs indicating rejected or failed voice-call sessions coinciding with resource exhaustion events

Detection Strategies

Monitor WebSocket connection metrics for unusual frame sizes or connection patterns to voice-call endpoints
Implement network-level inspection for oversized WebSocket frames targeting OpenClaw services
Configure resource monitoring alerts for memory and CPU spikes correlated with voice-call component activity
Deploy application-level logging to track pre-start validation failures and frame size anomalies

Monitoring Recommendations

Establish baseline metrics for normal WebSocket frame sizes in voice-call communications
Configure alerts for memory utilization exceeding thresholds on servers running OpenClaw voice-call services
Monitor connection rate limiting effectiveness and adjust thresholds based on attack patterns
Review server logs regularly for patterns indicating resource exhaustion attack attempts

How to Mitigate CVE-2026-41400

Immediate Actions Required

Update OpenClaw to version 2026.3.31 or later which contains the complete fix for this vulnerability
Implement network-level rate limiting for WebSocket connections to voice-call endpoints
Configure WebSocket frame size limits at the load balancer or reverse proxy level
Monitor server resources and implement automatic scaling or circuit breakers to handle potential attack traffic

Patch Information

The security patch is available in the GitHub Commit Update. The fix modifies the media-stream.ts file in the extensions/voice-call/src/ directory to properly reject oversized pre-start media frames before they are fully processed. Organizations should update to OpenClaw version 2026.3.31 or apply the commit 9abcfdadf591bf266d85fbdfe14ae833e557a110 to address this vulnerability.

Additional details are available in the GitHub Security Advisory and the VulnCheck Resource Consumption Advisory.

Workarounds

Deploy a Web Application Firewall (WAF) or reverse proxy configured to limit WebSocket frame sizes before they reach OpenClaw
Implement connection rate limiting at the network edge to reduce the effectiveness of DoS attacks
Consider disabling the voice-call component temporarily if not essential to operations until the patch can be applied
Use container or process resource limits to prevent a single service from consuming all available system resources

bash

# Configuration example - nginx WebSocket frame size limit
location /voice-call {
    proxy_pass http://openclaw_backend;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
    
    # Limit WebSocket frame buffer size
    proxy_buffer_size 8k;
    proxy_buffers 8 8k;
    
    # Connection rate limiting
    limit_req zone=voice_call_limit burst=10 nodelay;
}