Executive Summary

This vulnerability exists in the Rack Ruby web server interface where the method Rack::Request#POST reads the entire request body into memory for requests with Content-Type: application/x-www-form-urlencoded without enforcing any length limit. This means that very large request bodies can be fully loaded into memory, potentially exhausting system memory and causing a denial of service (DoS).

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Impact Analysis

The vulnerability can lead to denial of service (DoS) by exhausting the server's memory when processing large request bodies. This can cause the server to become unresponsive or crash, disrupting service availability.

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Detection Guidance

Detection can involve monitoring for unusually large HTTP POST requests with Content-Type: application/x-www-form-urlencoded that may cause memory exhaustion. Commands to inspect such requests depend on your environment; for example, using network packet capture tools like tcpdump or Wireshark to filter POST requests, or checking web server logs for large request bodies. However, specific commands are not provided in the available information.

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Mitigation Strategies

Immediate mitigation steps include upgrading Rack to version 2.2.20, 3.1.18, or 3.2.3 or later, which enforce form parameter limits to prevent unbounded reads. Additionally, configure your proxy or web server to enforce strict maximum body size limits, such as setting 'client_max_body_size' in Nginx or 'LimitRequestBody' in Apache.

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