CVE-2026-68579 in FreeRDP
Summary
by MITRE • 08/02/2026
FreeRDP before 3.30.0 (<= 3.29.0) contains a heap-based buffer overflow in the Windows clipboard client's CliprdrStream_Read function (client/Windows/wf_cliprdr.c). When an OLE paste consumer (e.g. explorer.exe) calls IStream::Read with a fixed-size buffer of cb bytes, CliprdrStream_Read requests file contents from the RDP server and then copies the response into the caller's buffer using the server-supplied length (req_fsize) instead of cb. A malicious or compromised RDP server can return an oversized CB_FILECONTENTS_RESPONSE, causing an out-of-bounds write of attacker-controlled data into the paste consumer's heap buffer when a user pastes server-offered clipboard file contents.
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Analysis
by VulDB Data Team • 08/02/2026
The vulnerability identified in FreeRDP versions prior to 3.30.0 represents a critical heap-based buffer overflow that occurs within the Windows clipboard client implementation. This flaw exists specifically in the CliprdrStream_Read function located at client/Windows/wf_cliprdr.c, where the software fails to properly validate buffer boundaries during clipboard data processing. The issue manifests when a remote desktop session attempts to handle file content transfers through the clipboard mechanism, creating a pathway for malicious data injection that can compromise system integrity.
The technical exploitation of this vulnerability stems from improper input validation within the clipboard handling code path. When an OLE paste operation is initiated by applications such as explorer.exe, the system invokes IStream::Read with a predetermined buffer size cb. However, the CliprdrStream_Read function incorrectly uses the server-supplied file size parameter req_fsize for copying operations instead of the actual caller buffer size cb. This mismatch creates a scenario where attacker-controlled data from a malicious RDP server can overflow the allocated heap buffer, resulting in out-of-bounds write operations that may corrupt adjacent memory regions.
From an operational perspective, this vulnerability presents significant security risks to organizations relying on FreeRDP for remote desktop connections. The attack vector requires a compromised or malicious RDP server to deliver oversized clipboard responses, but once executed, it can lead to arbitrary code execution within the context of the paste consumer process. The heap corruption can potentially be leveraged to escalate privileges or cause application crashes that may facilitate further exploitation attempts. This vulnerability particularly affects Windows environments where clipboard functionality is actively used during remote desktop sessions.
The impact of this buffer overflow aligns with CWE-121, which addresses stack-based buffer overflow conditions, and more specifically relates to heap-based overflows under CWE-122. The vulnerability demonstrates characteristics consistent with ATT&CK technique T1059.007 for Windows Command Shell execution and T1566 for spearphishing attachments, as it can be exploited through malicious clipboard content delivery during remote desktop sessions. Organizations should prioritize immediate patching to version 3.30.0 or later, while implementing network segmentation controls to limit exposure to potentially compromised RDP servers. Additionally, monitoring for unusual clipboard activity and implementing application whitelisting measures can provide additional defense-in-depth strategies against exploitation attempts targeting this specific vulnerability.