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Not in CISA KEV
HIGH severity

CVE-2026-56189

HIGH

CVE-2026-56189 is a high-severity (CVSS 7.8) CWE-122 vulnerability in microsoft windows 10 21h2. O3 Security detects and blocks CVE-2026-56189 exploitation at runtime via eBPF exploit-chain detection and L7 egress monitoring, even on unpatched systems.

Heap-based buffer overflow in Microsoft Windows Media Foundation allows an unauthorized attacker to execute code locally.

Published
Jul 14, 2026
Updated
Jul 22, 2026
Affected
12 products
Patched
See advisory
Exploits
None indexed
Exploitation data as of Jul 22, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Description

Heap-based buffer overflow in Microsoft Windows Media Foundation allows an unauthorized attacker to execute code locally.

Affected Products

12 products · 15 configurations
OS
windows 10 21h2microsoft
< 10.0.19044.7548
range
OS
windows 10 22h2microsoft
< 10.0.19045.7548
range
OS
windows 10 1607microsoft
< 10.0.14393.9339
range
OS
windows 10 1809microsoft
< 10.0.17763.9020
range
OS
windows 11 24h2microsoft
< 10.0.26100.8875
range
OS
windows 11 25h2microsoft
< 10.0.26200.8875
range

Detection & mitigation playbook

Vendor / appliance
  1. Detect

    Inventory every microsoft windows 10 21h2 deployment and check each version against the affected-products list above. Because the exploit targets the running system rather than your application code, also watch for remote code execution at the network and runtime layer — O3 flags the exploit behaviour from runtime telemetry and egress traffic even before a vulnerable build is confirmed.

  2. Fix

    Apply the microsoft windows 10 21h2 security patch or hotfix for CVE-2026-56189 on the affected version, following the vendor advisory for your exact build.

  3. Workarounds

    Cut exposure now: restrict the management/admin interface to trusted networks, segment the device, and apply the vendor's recommended configuration mitigations and any WAF/IPS signature. O3's runtime protection blocks the exploit chain at execution, holding the line on unpatched or end-of-life systems until you can patch.

  4. How O3 protects you

    O3 detects and blocks CVE-2026-56189 exploitation at runtime: eBPF exploit-chain detection, plus L7 egress monitoring that catches the post-exploitation callback and severs the attacker's outbound channel.

Tailored to CVE-2026-56189. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

Heap-based buffer overflow in Microsoft Windows Media Foundation allows an unauthorized attacker to execute code locally.
O3 Security · Runtime Protection

Is CVE-2026-56189 being exploited in your environment?

O3's eBPF runtime sensors and L7 egress monitoring detect and block the CVE-2026-56189 exploit chain at execution — protecting unpatched and end-of-life systems until the vendor patch is applied.