Windows Work Folders: Use after free allows local privilege escalation

Summary

A use-after-free flaw in the Windows Work Folders component allows an attacker to elevate privileges on the local system. The attacker needs local access and a valid low-privileged account, and the attack is complex to carry out. The flaw is a post-compromise risk and is not reachable from the internet.

Affected

• Windows 10 Version 1809 (10.0.17763.0 to < 10.0.17763.9376)
• Windows 10 Version 21H2 (10.0.19044.0 to < 10.0.19044.7807)
• Windows 10 Version 22H2 (10.0.19045.0 to < 10.0.19045.7807)
• Windows 11 Version 23H2 (10.0.22631.0 to < 10.0.22631.7652)
• Windows 11 Version 24H2 (10.0.26100.0 to < 10.0.26100.9711)
• Windows 11 Version 25H2 (10.0.26200.0 to < 10.0.26200.9711)
• Windows 11 Version 26H1 (10.0.28000.0 to < 10.0.28000.3231)
• Windows 11 Version 26H2 (10.0.26300.0 to < 10.0.26300.9711)
• Windows Server 2019 incl. Server Core (10.0.17763.0 to < 10.0.17763.9376)
• Windows Server 2025 incl. Server Core (10.0.26100.0 to < 10.0.26100.33650)

Fixed in

• Windows 10 1809: 10.0.17763.9376 (KB5126651 according to third-party listings, not yet verified against Microsoft)
• Windows 10 21H2: 10.0.19044.7807
• Windows 10 22H2: 10.0.19045.7807
• Windows 11 23H2: 10.0.22631.7652
• Windows 11 24H2, 25H2, 26H2: 10.0.26100.9711, 10.0.26200.9711, 10.0.26300.9711
• Windows 11 26H1: 10.0.28000.3231
• Windows Server 2019: 10.0.17763.9376
• Windows Server 2025: 10.0.26100.33650
• Release date of the update: October 13, 2026

Workaround

Unknown. No vendor workaround was found in the sources reviewed. If Work Folders is not used, disabling the feature reduces the attack surface until patching is complete (our suggestion, not a vendor recommendation).

Exploitation

• Microsoft rates exploitability as Unproven.
• CISA SSVC: exploitation none, automatable no, technical impact total.
• EPSS 0.00264.
• No public exploit code and no known in-the-wild exploitation in the sources reviewed. This means nothing is known in these sources, not that exploitation is ruled out.

Our recommendation

• Install the October 2026 security update for each affected build as part of the regular monthly patch cycle, and prioritise multi-user systems and servers where Work Folders is enabled.
• Check the Windows build inventory, especially Windows 10 1809 and Windows Server 2019, which are often still used on LTSC systems.
• Remove Windows 10 Home/Pro 1809 systems, which are out of support.
• Limit local logon on terminal servers and shared systems, and monitor for unusual privilege changes.

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: CVE-2026-70045 msrc.microsoft.com
• Vulners CVE list entry (CNA data) vulners.com
• Vulners MSCVE entry vulners.com
• Vulners NVD entry (EPSS) vulners.com

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 4 Nov 2026, 09:18.