Memory Exhaustion in FreeRDP via Unbounded Reassembly

Executive Summary

This vulnerability is an unbounded reassembly flaw in FreeRDP versions 2.0.0 through 3.31.0. It occurs in the WTSProcessChannelData function where cumulative fragment sizes are not limited during static virtual channel message processing. Authenticated clients can exploit this by sending endless fragments without the LAST flag, causing the server to exhaust memory.

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Detection Guidance

Monitor FreeRDP server memory usage for unusual spikes. Check for incomplete static virtual channel messages by inspecting network traffic for fragmented RDP packets without the LAST flag. Use tools like Wireshark to filter RDP traffic and look for repeated fragments from authenticated clients.

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Impact Analysis

This flaw can lead to denial-of-service conditions by consuming server memory, potentially crashing services or degrading performance. Attackers with valid credentials can trigger it, causing resource exhaustion proportional to traffic sent.

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Compliance Impact

This vulnerability could impact compliance with GDPR and HIPAA by enabling denial-of-service attacks that disrupt system availability. GDPR requires maintaining data processing systems securely, while HIPAA mandates reliable access to protected health information. Memory exhaustion could lead to service disruptions, potentially violating availability requirements in these regulations.

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Mitigation Strategies

Upgrade FreeRDP to version 3.32.0 or later to address the unbounded reassembly flaw. Implement network-level controls to limit RDP traffic rates and block suspicious fragmented messages. Monitor server memory usage and set alerts for abnormal consumption patterns.

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