Heap-based buffer overflow in Microsoft Windows and Windows Server - CVE-2026-20868
Published: January 13, 2026
Vulnerability identifier: #VU121271
CSH Severity: High
CVSS v4: 8.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-20868
CWE-ID: CWE-122
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to execute arbitrary code on the target system.
The vulnerability exists due to a boundary error in Windows Routing and Remote Access Service (RRAS). A remote attacker can trick a victim into sending a request to a malicious server, trigger a heap-based buffer overflow and execute arbitrary code on the target system.
Successful exploitation of this vulnerability may result in complete compromise of vulnerable system.
Affected software
Microsoft Windows
Windows Server
Windows Server
How to mitigate CVE-2026-20868
Install updates from vendor's website.
Microsoft Windows - addressed in versions 10 21H2 10.0.19044.6809, 10 22H2 10.0.19045.6809, 10 1607 10.0.14393.8783, 10 1809 10.0.17763.8276, 11 23H2 10.0.22631.6491, 11 24H2 10.0.26100.3223, 11 24H2 10.0.26100.7623
Windows Server - addressed in versions 2008 R2 6.1.7601.28117, 2008 6.0.6003.23717, 2012 R2 6.3.9600.22968, 2012 6.2.9200.25868, 2016 10.0.14393.8783, 2019 10.0.17763.8276, 2022 23H2 10.0.25398.2092, 2022 10.0.20348.4648, 2025 10.0.26100.7623, 2025 10.0.26100.32230
Windows Server - addressed in versions 2008 R2 6.1.7601.28117, 2008 6.0.6003.23717, 2012 R2 6.3.9600.22968, 2012 6.2.9200.25868, 2016 10.0.14393.8783, 2019 10.0.17763.8276, 2022 23H2 10.0.25398.2092, 2022 10.0.20348.4648, 2025 10.0.26100.7623, 2025 10.0.26100.32230