CVE-2026-20837

Published: Jan 13, 2026Modified: Jan 15, 2026

7.8

Vector

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Exploitability: 1.8 / Impact: 5.9

Source: secure@microsoft.com

Description

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

Affected (11)

Products: Microsoft: Windows 10 1809, Windows 10 21h2, Windows 10 22h2, Windows 11 23h2, Windows 11 24h2, Windows 11 25h2, Windows Server 2019, Windows Server 2022, Windows Server 2022 23h2, Windows Server 2025

10 products

Windows 10 1809

Windows 10 21h2

Windows 10 22h2

Windows 11 23h2

Windows 11 24h2

Windows 11 25h2

Windows Server 2019

Windows Server 2022

Windows Server 2022 23h2

Windows Server 2025

Configuration A

11 vulnerable

Vulnerable Software	Affected Versions
Microsoft Windows 10 1809	Before 10.0.17763.8276
Microsoft Windows 10 1809	Before 10.0.17763.8276
Microsoft Windows 10 21h2	Before 10.0.19044.6809
Microsoft Windows 10 22h2	Before 10.0.19045.6809
Microsoft Windows 11 23h2	Before 10.0.22631.6491
Microsoft Windows 11 24h2	Before 10.0.26100.7623
Microsoft Windows 11 25h2	Before 10.0.26200.7623
Microsoft Windows Server 2019	Before 10.0.17763.8276
Microsoft Windows Server 2022	Before 10.0.20348.4648
Microsoft Windows Server 2022 23h2	Before 10.0.25398.2092
Microsoft Windows Server 2025	Before 10.0.26100.32230

Related CWEs

Heap-based Buffer Overflow

A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().

References (1)

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20837

Source: secure@microsoft.com

Vendor Advisory

Timeline

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