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Windows Media Foundation: Local privilege escalation via use after free

CVE-2026-102201High 7.8

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Summary

A use-after-free vulnerability (CWE-416) in the Microsoft Windows Media Foundation component allows a local attacker with low privileges to elevate their privileges. The attacker first needs local code execution or a low-privileged account. The flaw is not reachable from the internet; the main risk is chaining it with another bug after a phishing or malware foothold, especially on terminal or RDS servers.

Affected

  • Windows 10 Version 1809 and Windows Server 2019 (including Server Core): 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

Fixed in

  • Windows 10 1809 and Server 2019: build 10.0.17763.9376 via KB5126651 (released 13 Oct 2026)
  • Out-of-band follow-up for Windows 10 1809 and Server 2019: KB5134124 (build 17763.9378, released 26 Oct 2026), recommended
  • Other branches: fixed builds as listed under affected, from the October 2026 updates
  • Mapping of this CVE to KB5126651 is based on CNA build data and a third-party reference; not confirmed in Microsoft's KB text

Workaround

Unknown.

  • No official workaround or mitigation found. Patching is the remedy.

Exploitation

  • In the wild: Unknown. No source found that names this CVE as exploited.
  • Public proof of concept: none found.
  • CISA SSVC: exploitation none, automatable no, technical impact total.
  • EPSS: 0.00318 (very low).

Our recommendation

  • Install KB5134124 on all affected Windows 10 1809 and Server 2019 hosts; at least install KB5126651.
  • Install the October 2026 updates for all other affected Windows 10 and Windows 11 branches.
  • Prioritise RDS/terminal servers and multi-user servers.
  • Check that all hosts run a supported Windows branch; Windows 10 1809 and Server 2019 must be patched.
  • Verify the fixed build list against the MSRC entry before closing the ticket.
  • Monitor for unusual privilege changes on hosts with many user sessions.

Information from Microsoft (Patch Tuesday October 2026)

Severity (Microsoft)
Important
Impact
Elevation of privilege – Microsoft Windows Media Foundation
Status on Patch Tuesday
Neither exploited nor publicly disclosed
Exploitability assessment
Exploitation less likely
Product family
Windows, Windows ESU (Extended Security Updates)
Updates (KB)
KB5126651, KB5126657, KB5126653, KB5127648, KB5127646

Entry in the Microsoft Security Update Guide

Public exploits

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

Research sources

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, 05:14.

Original description (NVD)

Use after free in Microsoft Windows Media Foundation allows an authorized attacker to elevate privileges locally.

NVD references (1)

Sources

The tracker combines official, freely usable data sources – updated continuously:

This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.

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