A critical vulnerability, CVE-2026-68579 (CVSS 9.6), has been identified in FreeRDP, a popular open-source implementation of the Remote Desktop Protocol (RDP). This issue affects the Windows client specifically in versions prior to 3.30.0.
The vulnerability permits a remote, unauthenticated attacker—controlling a malicious RDP server—to execute arbitrary code on the victim's machine. The attack vector is particularly insidious because it requires no user interaction beyond establishing a standard RDP connection; once the connection is made, the server can trigger the overflow through clipboard redirection mechanisms.
Given the widespread use of FreeRDP in cross-platform remote administration and bridge tools, Security Arsenal strongly recommends immediate patching for all environments utilizing this library.
Technical Analysis
Affected Component:
The vulnerability resides in client/Windows/wf_cliprdr.c, specifically within the CliprdrStream_Read function. This component handles the Virtual Channel Clipboard Redirection (Cliprdr), which allows users to copy and paste files/data between the local client and the remote RDP session.
Vulnerability Mechanics:
- The Trigger: When an OLE paste consumer on the client side (commonly
explorer.exe) callsIStream::Read, it passes a fixed-size buffer defined bycbbytes. - The Flaw: The
CliprdrStream_Readfunction requests file contents from the RDP server. However, when copying the response into the caller's buffer, it incorrectly utilizes the server-supplied length (req_fsize) rather than the client-supplied buffer size (cb). - The Exploit: A malicious RDP server can respond with a
CB_FILECONTENTS_RESPONSEpacket where the declared file size is significantly larger than the allocated local buffer. - Impact: This results in a heap-based buffer overflow, allowing an attacker to write attacker-controlled data out-of-bounds, leading to Remote Code Execution (RCE) with the privileges of the FreeRDP client.
Affected Versions:
- FreeRDP versions before 3.30.0 (<= 3.29.0) on Windows.
Exploitation Status: While active exploitation in the wild has not been explicitly confirmed at the time of publication, the severity (CVSS 9.6), the ease of exploitation (network-facing), and the availability of proof-of-concept code make functional exploitation highly likely in the near term.
Detection & Response
Sigma Rules
The following Sigma rules identify the execution of the vulnerable FreeRDP client binary (wfreerdp.exe) and potential application crashes indicative of heap corruption attempts.
---
title: FreeRDP Client Execution
id: 8a4d2e11-5f7a-4c9d-8b2a-1c3d4e5f6789
status: experimental
description: Detects execution of the FreeRDP Windows client (wfreerdp.exe), which may be vulnerable to CVE-2026-68579 if outdated.
references:
- https://nvd.nist.gov/vuln/detail/CVE-2026-68579
author: Security Arsenal
date: 2026/04/14
tags:
- attack.initial_access
- attack.t1133
logsource:
category: process_creation
product: windows
detection:
selection:
Image|endswith:
- '\wfreerdp.exe'
- '\wfreerdp-connect.exe'
condition: selection
falsepositives:
- Legitimate administrative use of FreeRDP
level: low
---
title: Potential FreeRDP Heap Overflow Crash
id: 9b5e3f22-6g8b-5d0e-9c3b-2d4e5f6g7890
status: experimental
description: Detects application errors (crashes) involving the FreeRDP client or its clipboard module, potentially indicating exploit attempts for CVE-2026-68579.
references:
- https://nvd.nist.gov/vuln/detail/CVE-2026-68579
author: Security Arsenal
date: 2026/04/14
tags:
- attack.exploitation
- attack.t1203
logsource:
product: windows
service: application
definition: 'Requirements: Microsoft-Windows-WER-Operational channel'
detection:
selection:
EventID: 1000 # Application Error
FaultingModuleName|contains:
- 'wf_cliprdr'
- 'wfreerdp'
condition: selection
falsepositives:
- Instability in the RDP connection due to network issues
level: high
KQL (Microsoft Sentinel)
Use this query to hunt for instances of FreeRDP connecting to external endpoints and correlate them with process creation.
// Hunt for FreeRDP execution and external network connections
let FreeRDPProcess =
DeviceProcessEvents
| where FolderPath endswith "\\wfreerdp.exe"
| project DeviceId, DeviceName, ProcessId, InitiatingProcessAccountName, ProcessCommandLine, Timestamp;
let FreeRDPNetwork =
DeviceNetworkEvents
| where InitiatingProcessFolderPath endswith "\\wfreerdp.exe"
| project DeviceId, RemoteUrl, RemoteIP, RemotePort, Timestamp;
FreeRDPProcess
| join (FreeRDPNetwork) on DeviceId, Timestamp
| project Timestamp, DeviceName, RemoteIP, RemoteUrl, ProcessCommandLine
| order by Timestamp desc
Velociraptor VQL
This artifact hunts for the presence of the FreeRDP executable on the disk and attempts to parse its file version to identify vulnerable instances (< 3.30.0).
-- Hunt for FreeRDP binaries and check version
SELECT FullPath, Mtime, Size,
parse_string(data=VersionInfo.Data, regex="FileVersion\\s*\\|\s*(?P<Version>[\\d.]+)").Version as FileVersion
FROM glob(globs="C:/Program Files/**/wfreerdp.exe")
JOIN foreach(row={
SELECT OSPath, Data FROM read_file filenames=FullPath
}, query={
SELECT FullPath, Data FROM scope()
}) ON FullPath = OSPath
WHERE FileVersion < "3.30.0"
Remediation Script (PowerShell)
This script checks for the presence of wfreerdp.exe in common locations and validates the version against the safe threshold (3.30.0).
# Check for vulnerable FreeRDP installations
$VulnerableVersions = @("3.0.0", "3.1.0", "3.2.0", "3.3.0", "3.4.0", "3.5.0", "3.6.0", "3.7.0", "3.8.0", "3.9.0", "3.10.0", "3.11.0", "3.12.0", "3.13.0", "3.14.0", "3.15.0", "3.16.0", "3.17.0", "3.18.0", "3.19.0", "3.20.0", "3.21.0", "3.22.0", "3.23.0", "3.24.0", "3.25.0", "3.26.0", "3.27.0", "3.28.0", "3.29.0")
$SafeVersion = [version]"3.30.0"
$PathsToCheck = @("C:\Program Files\FreeRDP", "C:\Program Files (x86)\FreeRDP", "$env:LOCALAPPDATA\FreeRDP")
$FoundVulnerable = $false
foreach ($Path in $PathsToCheck) {
if (Test-Path $Path) {
$ExePath = Join-Path -Path $Path -ChildPath "wfreerdp.exe"
if (Test-Path $ExePath) {
$FileInfo = Get-Item $ExePath
$VersionInfo = $FileInfo.VersionInfo.FileVersion
if ($VersionInfo) {
try {
$CurrentVersion = [version]$VersionInfo
if ($CurrentVersion -lt $SafeVersion) {
Write-Host "[ALERT] Vulnerable FreeRDP found at: $ExePath" -ForegroundColor Red
Write-Host "Current Version: $CurrentVersion (Required: >= $SafeVersion)" -ForegroundColor Red
$FoundVulnerable = $true
}
else {
Write-Host "[OK] FreeRDP at $ExePath is patched (Version: $CurrentVersion)" -ForegroundColor Green
}
}
catch {
Write-Host "[WARN] Could not parse version for $ExePath" -ForegroundColor Yellow
}
}
}
}
}
if (-not $FoundVulnerable) {
Write-Host "No vulnerable FreeRDP instances found in standard paths." -ForegroundColor Green
}
Remediation
- Patch Immediately: Update FreeRDP to version 3.30.0 or later. Official releases can be obtained from the FreeRDP GitHub repository.
- Workaround (Clipboard Redirection): If immediate patching is not feasible, disable clipboard redirection to prevent the malicious vector. This can be done by launching the client with the
/clipboardflag omitted or explicitly disabled depending on specific client configuration flags (e.g.,-driveor/clipboardarguments). - Network Segmentation: Restrict outbound RDP connections from client workstations. Ensure that RDP clients can only connect to known, trusted management jump hosts or internal VDI infrastructure, blocking direct connectivity to external or untrusted IPs.
- Vendor Review: If FreeRDP is embedded within third-party software, contact the vendor for a security update containing the patched library.
Related Resources
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