Heap-based buffer overflow in Microsoft Windows and Windows Server - CVE-2026-88240

Vulnerability identifier: #VU165577

CSH Severity: Medium

CVSS v4: 8.6 [CVSS:4.0/AV:A/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-88240

CWE-ID: CWE-122

Exploitation vector: Adjecent network

Exploit availability: No public exploit available

The vulnerability allows a remote user on the local network to escalate privileges to SYSTEM.

The vulnerability exists due to a heap-based buffer overflow in Windows DHCP Client when processing network input. A remote user on the local network can supply specially crafted input over an adjacent network to corrupt heap memory and escalate privileges to SYSTEM.

Microsoft Windows
Windows Server

Install security update from vendor's website.

Microsoft Windows - addressed in versions 10 21H2 10.0.19044.7846, 10 22H2 10.0.19045.7846, 10 1607 10.0.14393.9688, 10 1809 10.0.17763.9487, 11 23H2 10.0.22631.7711, 11 24H2 10.0.26100.9911, 11 24H2 10.0.26100.9974, 11 25H2 10.0.26200.9911, 11 25H2 10.0.26200.9974, 11 26H1 10.0.28000.3501
Windows Server - addressed in versions 2016 10.0.14393.9688, 2019 10.0.17763.9487, 2022 10.0.20348.5870, 2025 10.0.26100.33730, 2025 10.0.26100.33822

• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2026-88240

• Multiple vulnerabilities in Microsoft Windows