Microsoft Remote Desktop Client: Use-after-free leads to remote code execution

Summary

A use-after-free vulnerability (CWE-416) in the Remote Desktop Client (mstsc) of several Windows 10, 11 and Server versions allows an unauthorized attacker to execute code over the network. The CVSS vector requires high attack complexity and user interaction, for example luring a user into connecting to a malicious RDP host. No privileges are required. As of 2 Nov 2026, no in-the-wild exploitation and no public proof-of-concept code were found.

Affected

• Windows 10 Version 1607 (builds before 10.0.14393.9612)
• Windows 10 Version 1809 (builds before 10.0.17763.9376)
• Windows 10 Version 21H2 (builds before 10.0.19044.7807)
• Windows 10 Version 22H2 (builds before 10.0.19045.7807)
• Windows 11 Version 23H2 (builds before 10.0.22631.7652)
• Windows 11 Version 24H2 (builds before 10.0.26100.9711)
• Windows 11 Version 25H2 (builds before 10.0.26200.9711)
• Windows 11 Version 26H1 (builds before 10.0.28000.3231)
• Windows 11 Version 26H2 (builds before 10.0.26300.9711)
• Windows Server 2012 and 2012 R2, including Server Core (builds before 6.2.9200.26434 and 6.3.9600.23470)
• Windows Server 2016 (builds before 10.0.14393.9612)

Fixed in

• Security updates from October 2026 or later, which deliver the fixed builds listed in the Microsoft CNA record (for example 10.0.14393.9612 for 1607 and Server 2016, 10.0.17763.9376 for 1809, 10.0.19045.7807 for 22H2).
• KB numbers and build numbers from third-party sites are not yet verified against the Microsoft Security Update Guide.

Workaround

• No Microsoft workaround documented; the security update is the fix.
• Until patched (own assessment, not vendor guidance): avoid connecting to untrusted RDP hosts and do not open .rdp files from unknown senders.

Exploitation

• No in-the-wild exploitation found as of 2 Nov 2026.
• Not listed in CISA KEV (per OpenCVE).
• CISA SSVC: exploitation none, automatable no, technical impact total.
• No public proof-of-concept or exploit found; this is not proof that none exists.
• EPSS about 0.57%.

Our recommendation

• Install the October 2026 cumulative updates on all affected Windows 10, 11 and Server systems, verifying build numbers in the Microsoft Security Update Guide first.
• Prioritise Windows machines that users use to reach remote desktops or jump hosts.
• Check whether Windows 10 1607 and Server 2016 systems are still supported.
• Check RD Session Host and RD Gateway servers too; CVE-2026-69992 is a different server-side issue.
• Restrict RDP connections to trusted hosts and monitor for unusual RDP connections.

Public exploits iAttack code is publicly available (PoC on GitHub, Metasploit or Exploit-DB).

PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.

Research sources

• Microsoft Security Update Guide (vendor advisory) msrc.microsoft.com
• Vulners CVE List record (Microsoft CNA data) vulners.com
• Vulners NVD record vulners.com
• OpenCVE record app.opencve.io
• Tenable plugin list www.tenable.com
• Strix CVE summary www.strix.ai

Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 2 Nov 2026, 19:15.