Heap Out-of-Bounds Read in FreeRDP

Executive Summary

CVE-2026-109950 is a heap out-of-bounds read vulnerability in FreeRDP versions 3.0.0 through 3.31.1. A malicious RD Gateway can send consent or service messages with mismatched lengths between the outer MsgBytes value and the NDR string's ActualCount. The client uses the larger MsgBytes value during UTF-8 conversion but only validates the smaller NDR string length, causing it to read past the allocated buffer.

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Detection Guidance

Detecting this vulnerability requires monitoring FreeRDP client connections for crashes or unusual behavior when interacting with RD Gateway servers. Check FreeRDP client logs for heap out-of-bounds read errors or segmentation faults during UTF-8 conversion. Use network traffic analysis tools like Wireshark to inspect consent or service messages for mismatched MsgBytes and NDR string ActualCount values. Enable AddressSanitizer during FreeRDP compilation to catch out-of-bounds reads in real-time.

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Impact Analysis

This vulnerability can cause client connections to crash or become unavailable. Attackers controlling the RD Gateway can disrupt service by triggering heap out-of-bounds reads, though no code execution or data disclosure has been demonstrated. Users must interact with the malicious gateway for exploitation.

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Compliance Impact

This vulnerability primarily impacts client availability by causing crashes due to heap out-of-bounds reads, but does not directly lead to code execution or remote information disclosure. Compliance with standards like GDPR or HIPAA is not directly affected unless client disruptions impact data processing or availability requirements.

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Mitigation Strategies

Immediately upgrade FreeRDP to version 3.32.0 or later to patch the vulnerability. If upgrading is not possible, restrict access to RD Gateway servers by implementing strict network controls or disabling gateway functionality. Monitor client connections for signs of exploitation and apply network-level mitigations like TLS certificate pinning to prevent man-in-the-middle attacks.

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