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

Summary

A use-after-free (CWE-416) in the Remote Desktop Client of Windows allows an unauthorized attacker to execute code over the network. According to the CVSS vector (AV:N/AC:H/PR:N/UI:R), exploitation requires high complexity and user interaction, for example a user connecting to an attacker-controlled RDP endpoint. The Microsoft CNA record lists many Windows 10, Windows 11 and Windows Server builds as affected. No exploitation or public proof of concept was found at the time of research.

Affected

• Windows 10 Version 1607 and Windows Server 2016: before 10.0.14393.9612
• Windows 10 Version 1809: before 10.0.17763.9376
• Windows 10 Version 21H2: before 10.0.19044.7807
• Windows 10 Version 22H2: before 10.0.19045.7807
• Windows 11 Version 23H2: before 10.0.22631.7652
• Windows 11 Version 24H2: before 10.0.26100.9711
• Windows 11 Version 25H2: before 10.0.26200.9711
• Windows 11 Version 26H1: before 10.0.28000.3231
• Windows 11 Version 26H2: before 10.0.26300.9711
• Windows Server 2012 (including Server Core): before 6.2.9200.26434
• Windows Server 2012 R2 (including Server Core): before 6.3.9600.23470
• Note: the CPE in the input lists only Windows 10 1607; the CNA record is more complete. Secondary sources conflict on some build numbers.

Fixed in

• Fixed in the October 2026 Windows security updates. The fixed builds are the upper bounds listed above according to the CNA record.
• Build numbers from secondary sources conflict; verify them against the MSRC security update guide before relying on them.
• KB numbers for Windows 10 1607 could not be verified.

Workaround

• Unknown. No vendor workaround was found.
• Interim measure (not from a vendor source): until patched, connect RDP only to trusted hosts and do not open .rdp files or RDP links from unknown senders.

Exploitation

• No exploitation in the wild was found.
• No public proof of concept was found.
• CISA SSVC: exploitation none, automatable no, technical impact total.
• CISA KEV status was not verified.
• EPSS: 0.00569 (low probability).

Our recommendation

• Install the October 2026 Windows updates on all affected Windows 10, Windows 11 and Windows Server systems through the normal update cycle, and verify the builds against the MSRC table.
• Identify systems running Windows 10 1607 or Windows Server 2012/2012 R2 and check their lifecycle status; unsupported systems may receive no fix.
• Limit RDP client connections to trusted internal hosts and warn users about RDP files and links from unknown senders.
• Monitor for exploitation reports and a CISA KEV listing.

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, not verified) msrc.microsoft.com
• CNA record mirror (vulners) vulners.com
• NVD record mirror (vulners) vulners.com
• OpenCVE app.opencve.io
• Strix CVE mirror 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, 19:25.