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This Denial-of-Service (DoS) vulnerability affects React Router v7 when it operates in Framework Mode and also impacts Remix v2.9.0 and above when the Single Fetch feature is enabled. In these configurations, the `turbo-stream` package is used for data serialization. An attacker can exploit the underlying serialization algorithm by sending specially crafted, nested structures that are reflected in the server’s response. The algorithm lacks a throttling mechanism, which leads to CWE-770: Allocation of Resources Without Limits or Throttling. Upon decoding these nested inputs, the process consumes a disproportionate amount of CPU resources, effectively becoming a severe performance bottleneck. This uncontrolled resource consumption can degrade application performance to the point of making it completely unavailable to legitimate users.
The attack vector is entirely remote, requiring no authentication, and is executed via standard HTTP requests. The vulnerability exists in the vulnerable components because the serialization process attempts to recursively process the malicious input without any depth or size constraints. For an attacker, an unpatched server is highly exploitable, as a single request can be crafted to trigger the algorithmic slowdown. Crucially, the vulnerability does not impact applications using Declarative Mode (<BrowserRouter>) or Data Mode (createBrowserRouter/<RouterProvider>), as these modes do not utilize the same server-side serialization pipeline.
DailyCVE Form:
Platform: React Router / Remix
Version: 7.0.0 < 7.14.0
Vulnerability: DoS (Unbounded Allocation)
Severity: High
Date: 2026-06-02
Prediction: Patch expected: 2026-06-02
What Undercode Say:
Analytics and system status can be monitored using tools like `top` and `htop` to watch for CPU spikes, while `lsof` can track unexpected connection buildups on the Node.js process.
1. Monitor CPU usage to detect resource exhaustion caused by a single-fetch request top -p $(pgrep -d',' node) 2. Use lsof to list open network connections and detect a backlog of connections hitting the Node.js server lsof -i :3000 3. Simulate a basic fetch to a vulnerable endpoint (e.g., __manifest) with shell scripting Note: A real payload would contain deeply nested structures to trigger the bug. for i in {1..100}; do curl -s http://localhost:3000/__manifest -o /dev/null & done
Exploit:
An attacker would craft an HTTP GET request targeting the `__manifest` endpoint or a Single Fetch route. The payload contains a JavaScript object with an extremely high level of nesting. When the `turbo-stream` encoder processes this deeply nested data for the server response, it triggers the vulnerability due to the lack of recursion limits. This degrades server performance and can lead to a complete outage.
Protection:
- Upgrade Packages: Immediately update your packages to the patched versions: `react-router` to `v7.14.0` or later, or `@remix-run/server-runtime` to `v2.17.5` or later.
- Apply Network Controls: Implement strict rate limiting on the `__manifest` endpoint. Isolate or disable the endpoint if an immediate upgrade is impossible.
- Monitor and Throttle: Actively monitor server logs for anomalous request patterns targeting the vulnerable endpoints and enforce request size and depth throttling.
Impact:
- Integrity Impact: None. The attack is a pure Denial-of-Service and does not allow for data manipulation.
- Availability Impact: High. The vulnerability leads to significant response time degradation and can completely exhaust server resources, making the web application unavailable.
- Access Complexity: Low. The attack is remotely exploitable over a network and requires no authentication or prior access.
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Sources:
Reported By: github.com
Extra Source Hub:
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