Windows Text Services Framework: Privilege escalation via TOCTOU race condition

Summary

A time-of-check time-of-use (TOCTOU) race condition in the Windows Text Services Framework allows a local attacker to elevate privileges. The attacker needs an existing low-privileged account or code execution on the machine, and the attack is not exploitable remotely. Successful exploitation can grant SYSTEM or administrator rights, which would compromise the whole system.

Affected

• Windows 10 Version 1607 and Windows Server 2016 (including Server Core): builds before 10.0.14393.9688
• Windows 10 Version 1809 and Windows Server 2019 (including Server Core): builds before 10.0.17763.9487
• Windows 10 Version 21H2: builds before 10.0.19044.7846
• Windows 10 Version 22H2: builds before 10.0.19045.7846
• Windows 11 Version 23H2: builds before 10.0.22631.7711
• Windows 11 Version 24H2 and 25H2, Windows 11 Version 26H2: builds before 10.0.26100.9974, 10.0.26200.9974 and 10.0.26300.9974
• Windows 11 Version 26H1: builds before 10.0.28000.3501
• Windows Server 2022: builds before 10.0.20348.5870
• Affected ranges are taken from Microsoft's CVE record; confirm on the MSRC page.

Fixed in

• Install the Microsoft security update that brings the systems to the fixed builds listed above (the November 2026 security update according to the research notes).
• KB number: Unknown.

Workaround

Unknown.

Exploitation

• No evidence of exploitation in the wild found.
• No public proof of concept found.
• CISA SSVC: Exploitation none, Automatable no, Technical Impact total.
• Microsoft's exploit maturity rating: Unproven.

Our recommendation

• Install the Microsoft security update on all affected Windows systems in the normal monthly patch cycle, with priority on shared machines and Windows 10 builds still in use.
• Verify the affected builds and KB numbers on the MSRC advisory page before rollout.
• Limit local accounts and privileges, and monitor for unexpected privilege escalation.
• NVD status is Awaiting Analysis; the CVSS 7.0 score is Microsoft's own and may be rescored.

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-2026-119931 msrc.microsoft.com
• CVE Record CVE-2026-119931 (CNA: Microsoft) www.cve.org

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 11 Nov 2026, 08:27.