CVE-2026-67305 in FreeRDP
Summary
by MITRE • 08/01/2026
FreeRDP Windows client before 3.29.0 contains a heap buffer overflow vulnerability in the clipboard virtual channel when processing CLIPRDR_FILE_CONTENTS_RESPONSE PDUs without validating the server-provided size against the destination buffer. A malicious RDP server can send a response with a data payload significantly larger than requested, causing arbitrary heap memory corruption that may enable remote code execution when a user performs a paste operation.
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Analysis
by VulDB Data Team • 08/01/2026
This vulnerability exists within the FreeRDP Windows client software version 3.29.0 and earlier, representing a critical heap buffer overflow flaw in the clipboard virtual channel implementation. The issue specifically manifests when processing CLIPRDR_FILE_CONTENTS_RESPONSE protocol data units without proper validation of server-provided data sizes against destination buffer boundaries. The vulnerability stems from inadequate input sanitization within the clipboard handling mechanism that processes remote desktop protocol data.
The technical exploitation occurs through a malicious RDP server that can craft specially crafted CLIPRDR_FILE_CONTENTS_RESPONSE PDUs containing oversized data payloads. When the vulnerable FreeRDP client receives such a response, it attempts to copy the excessive data into a pre-allocated buffer without verifying that the source data length fits within the allocated memory space. This fundamental lack of bounds checking creates a classic heap-based buffer overflow condition where arbitrary memory locations become corrupted.
The operational impact of this vulnerability extends beyond simple memory corruption, as it can potentially enable remote code execution when users perform paste operations within the RDP session. The heap corruption occurs during clipboard data processing, and the malicious server can manipulate memory layout to achieve arbitrary code execution in the context of the FreeRDP client process. This makes the vulnerability particularly dangerous in environments where users may unknowingly paste content from untrusted sources.
From a cybersecurity perspective, this vulnerability aligns with CWE-121 Heap-based Buffer Overflow and represents a significant risk in enterprise environments where RDP is commonly used for remote access. The attack vector requires a malicious RDP server to be present in the network, typically through compromised systems or man-in-the-middle scenarios. This weakness can be classified under ATT&CK technique T1059 Command and Scripting Interpreter, specifically when adversaries leverage clipboard manipulation as part of their exploitation strategy.
The recommended mitigation involves upgrading to FreeRDP version 3.29.0 or later, which includes proper bounds checking for clipboard data processing. Organizations should also implement network monitoring to detect anomalous RDP server behavior and consider deploying additional endpoint protection measures. Security teams should review their remote desktop usage policies and ensure that only trusted RDP servers are accessed, particularly in high-value environments where the risk of exploitation is elevated.