CVE-2026-24678: FreeRDP Use After Free Vulnerability

CVE-2026-24678 Overview

CVE-2026-24678 is a Use After Free vulnerability in FreeRDP, a free implementation of the Remote Desktop Protocol. Prior to version 3.22.0, a capture thread sends sample responses using a freed channel callback after a device channel close, leading to a use after free condition in the ecam_channel_write function. This memory corruption vulnerability can be exploited remotely over the network without requiring authentication.

Critical Impact

Remote attackers can exploit this use after free condition to cause denial of service through memory corruption when FreeRDP processes malicious RDP sessions.

Affected Products

• FreeRDP versions prior to 3.22.0
• Systems utilizing FreeRDP for Remote Desktop Protocol connections
• Applications and services built on FreeRDP libraries

Discovery Timeline

• 2026-02-09 - CVE-2026-24678 published to NVD
• 2026-02-10 - Last updated in NVD database

Technical Details for CVE-2026-24678

Vulnerability Analysis

This vulnerability is classified as CWE-416 (Use After Free), a memory corruption flaw that occurs when a program continues to use a pointer after it has been freed. In the context of FreeRDP, the issue specifically affects the enhanced camera (ecam) channel functionality. When a device channel is closed, the associated callback structure is freed, but a separate capture thread may continue to reference and use this deallocated memory when attempting to send sample responses.

The vulnerability is network-exploitable, meaning an attacker can trigger this condition remotely without requiring any user interaction or prior authentication. The primary impact is on system availability, as exploitation can lead to crashes and denial of service conditions.

Root Cause

The root cause of this vulnerability lies in improper synchronization between the channel close operation and the capture thread's use of channel callbacks. When a device channel close event occurs, the callback structure associated with ecam_channel_write is deallocated. However, the capture thread that processes sample responses maintains a stale reference to this freed memory. Without proper lifetime management or synchronization mechanisms, the capture thread attempts to invoke the freed callback, resulting in a use after free condition.

Attack Vector

The attack vector for CVE-2026-24678 is network-based. An attacker can exploit this vulnerability by:

1. Establishing an RDP connection to a vulnerable FreeRDP instance
2. Initiating an enhanced camera (ecam) channel session
3. Timing the closure of the device channel while the capture thread is actively processing sample responses
4. The race condition causes the capture thread to access the freed channel callback
5. This triggers the use after free in ecam_channel_write, potentially causing a crash

The vulnerability occurs in the ecam_channel_write function where the capture thread attempts to write sample responses using a channel callback that has already been freed due to a device channel close operation. This creates a race condition between thread execution and resource deallocation. For detailed technical information, see the FreeRDP Security Advisory.

Detection Methods for CVE-2026-24678

Indicators of Compromise

• Unexpected crashes or segmentation faults in FreeRDP processes during RDP sessions
• Core dumps showing memory access violations in ecam_channel_write or related camera channel functions
• Abnormal termination of RDP connections during camera device channel operations

Detection Strategies

• Monitor FreeRDP process stability and log unexpected terminations with memory corruption signatures
• Implement application-level monitoring to detect repeated crashes in RDP session handlers
• Deploy endpoint detection solutions capable of identifying use after free exploitation patterns
• Review system logs for FreeRDP crash events correlating with camera channel activity

Monitoring Recommendations

• Enable verbose logging for FreeRDP to capture channel operation events and potential error conditions
• Monitor network traffic for unusual RDP session patterns that may indicate exploitation attempts
• Implement crash analysis tools to automatically collect and analyze FreeRDP core dumps
• Set up alerts for repeated FreeRDP service restarts or failures

How to Mitigate CVE-2026-24678

Immediate Actions Required

• Upgrade FreeRDP to version 3.22.0 or later immediately
• If immediate patching is not possible, consider restricting network access to FreeRDP services
• Review and limit which systems can initiate RDP connections to vulnerable instances
• Enable enhanced monitoring on systems running vulnerable FreeRDP versions

Patch Information

The vulnerability has been fixed in FreeRDP version 3.22.0. The patch addresses the synchronization issue between the capture thread and channel close operations, ensuring that channel callbacks are not accessed after being freed. The fix is available in commit f3ab1a16139036179d9852745fdade18fec11600. Organizations should update to version 3.22.0 or apply the patch from the official FreeRDP repository.

Workarounds

• Disable enhanced camera (ecam) channel support if not required for business operations
• Implement network segmentation to limit exposure of FreeRDP services to untrusted networks
• Use firewall rules to restrict RDP access to known and trusted IP addresses only
• Consider using alternative RDP implementations while awaiting patch deployment

# Check current FreeRDP version
xfreerdp --version

# Update FreeRDP on Debian/Ubuntu systems
sudo apt update && sudo apt install freerdp2-x11

# Verify updated version (should be 3.22.0 or later)
xfreerdp --version