CVE-2026-66401 in FreeRDP
Summary
by MITRE • 08/01/2026
FreeRDP before 3.29.0 contains an out-of-bounds heap read vulnerability in the UVC H.264 extension-unit parser that fails to validate descriptor length before accessing the GUID field. A local attacker with a malicious USB video camera can trigger a heap read beyond allocated bounds during camera stream setup, causing denial of service.
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Analysis
by VulDB Data Team • 08/01/2026
The vulnerability under examination represents a critical out-of-bounds heap read condition within FreeRDP versions prior to 3.29.0, specifically impacting the UVC H.264 extension-unit parser component. This issue arises from inadequate validation of descriptor length parameters before accessing memory locations, creating a scenario where malicious input can cause unintended memory access patterns. The vulnerability is particularly concerning as it exists within the USB video class streaming setup process, making it exploitable through physical hardware manipulation rather than network-based attacks.
The technical flaw manifests in the parser's failure to properly validate the length field of UVC extension unit descriptors before attempting to read the GUID field from heap-allocated memory. This primitive validation oversight allows an attacker to craft malicious USB video camera devices that contain malformed descriptor structures with intentionally incorrect length values. When FreeRDP processes these descriptors during camera stream initialization, the parser attempts to access memory locations beyond the allocated buffer boundaries, resulting in heap read violations that can trigger application crashes or system instability.
From an operational perspective, this vulnerability creates a significant denial of service risk for systems utilizing FreeRDP for remote desktop connections with USB video device support. The attack requires physical proximity and local access to the target system, as the malicious USB camera must be connected directly to establish the vulnerable condition. However, the impact extends beyond simple service disruption since such vulnerabilities can potentially be leveraged in combination with other exploits to achieve more sophisticated attack vectors, particularly in environments where remote desktop services are exposed to untrusted users or networks.
The vulnerability aligns with CWE-129, which addresses validation of input length before accessing memory resources, and demonstrates how insufficient bounds checking in device enumeration processes can create exploitable conditions. From an ATT&CK framework perspective, this vulnerability falls under the T1059.007 technique for command and script interpreter usage, as the exploitation requires legitimate system interaction with USB video devices but leverages malformed descriptors to achieve unintended behavior. The attack surface is particularly relevant in enterprise environments where remote desktop protocols are extensively used alongside USB device redirection features.
Mitigation strategies should prioritize immediate patching of FreeRDP installations to version 3.29.0 or later, which includes proper descriptor length validation mechanisms. System administrators should implement USB device access controls through group policies and device whitelisting to prevent unauthorized USB devices from connecting to systems running remote desktop services. Network segmentation and monitoring should be enhanced to detect anomalous USB device connection patterns that could indicate exploitation attempts. Additionally, organizations should consider implementing runtime protections such as heap integrity checks and address space layout randomization to reduce the effectiveness of potential exploitation attempts while maintaining system stability during the patching process.