Memory Exhaustion in FreeRDP Proxy via RDPDR Fragment Reassembly

Executive Summary

FreeRDP versions from 3.0.0-beta1 to 3.32.0 have a flaw in the proxy where it fails to enforce size limits when reassembling RDPDR channel fragments. Attackers can send a FIRST fragment followed by continuation fragments without a LAST fragment, causing the proxy's memory to grow uncontrollably and eventually exhaust system resources.

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Detection Guidance

Detecting this vulnerability requires monitoring FreeRDP proxy instances for abnormal memory usage or fragmented RDPDR channel traffic. Check for processes consuming excessive memory or logs indicating incomplete fragment reassembly. Use tools like 'top', 'htop', or 'ps' to monitor memory usage and 'tcpdump' or 'Wireshark' to inspect network traffic for fragmented RDPDR packets.

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Impact Analysis

This vulnerability can lead to denial-of-service conditions where the FreeRDP proxy crashes or becomes unresponsive due to memory exhaustion. It may disrupt remote desktop services and affect the availability of systems relying on FreeRDP for remote access.

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Compliance Impact

This vulnerability could lead to denial-of-service conditions in FreeRDP proxies, potentially disrupting services handling sensitive data. While not directly violating GDPR or HIPAA, such disruptions may impact availability of systems processing personal or health data, indirectly affecting compliance with availability requirements under these regulations.

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Mitigation Strategies

Immediately update FreeRDP to version 3.32.0 or later to address the issue. If updating is not possible, restrict network access to the FreeRDP proxy or disable the RDPDR channel if not required. Monitor memory usage closely and consider implementing rate limiting on incoming connections.

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