Windows Telephony Service: Elevation of privilege via use after free

Summary

A use-after-free flaw (CWE-416) in the Windows Telephony Service allows a local attacker with low privileges to elevate their rights, potentially to SYSTEM. Exploitation requires local access, high attack complexity and no user interaction. The vulnerability is not directly reachable from the internet, but it matters on shared or multi-user Windows systems where users have local logon.

Affected

• Windows 10 Version 1607, 1809, 21H2, 22H2
• Windows 11 Version 23H2, 24H2, 25H2, 26H1, 26H2
• Windows Server 2016, 2019, 2022 (including Server Core installations)
• Affected build ranges are listed in the CVE record (CNA: Microsoft). Exact per-product builds must be checked on MSRC.

Fixed in

• Fixed in the Microsoft cumulative updates released on November 10, 2026. The first fixed builds are given in the CVE record as the upper bound of each affected range, for example 10.0.14393.9688 for Windows 10 1607 and Windows Server 2016, and 10.0.17763.9487 for Windows 10 1809 and Windows Server 2019.
• KB article numbers: Unknown. Check the MSRC Security Update Guide for each product.

Workaround

Unknown. No workaround was found in the sources. Patching is the primary remediation.

Exploitation

• Microsoft marks the vulnerability as not exploited at disclosure.
• The CVSS exploit code maturity is 'unproven' (E:U).
• No public proof-of-concept exploit was found at the time of writing.
• CISA SSVC assessment: exploitation none, not automatable, total technical impact.

Our recommendation

• Inventory all Windows 10, Windows 11 and Windows Server systems and check their build numbers against the MSRC page.
• Install the November 2026 cumulative update on workstations and servers in the next regular Patch Tuesday cycle, and prioritise multi-user servers, RDS/terminal servers and shared PCs.
• Restrict local logon on shared hosts where possible.
• Check whether the Telephony Service is running on each host, as this determines exposure.
• Monitor MSRC and CISA KEV for changes, as the CVE was published recently.

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-2026-108413 msrc.microsoft.com
• CVE Record: CVE-2026-108413 www.cve.org
• Strix CVE tracker: CVE-2026-108413 (third-party, version list unverified) 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 11 Nov 2026, 09:28.