Integer overflow in Microsoft Windows and Windows Server - CVE-2026-69521

Vulnerability identifier: #VU154399

CSH Severity: High

CVSS v4: 8.4 [CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-69521

CWE-ID: CWE-190

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to execute arbitrary code.

The vulnerability exists due to integer overflow or wraparound in Windows iSCSI when handling network calls to endpoints. A remote attacker can call arbitrary endpoints over a network to execute arbitrary code.

User interaction is required for successful exploitation.

Microsoft Windows
Windows Server

Install security update from vendor's website.

Microsoft Windows - addressed in versions 10 21H2 10.0.19044.7725, 10 22H2 10.0.19045.7725, 10 1607 10.0.14393.9512, 10 1809 10.0.17763.9245, 11 23H2 10.0.22631.7582, 11 24H2 10.0.26100.9445, 11 25H2 10.0.26200.9445, 11 26H1 10.0.28000.2954
Windows Server - addressed in versions 2012 R2 6.3.9600.23398, 2012 6.2.9200.26349, 2016 10.0.14393.9512, 2019 10.0.17763.9245, 2022 10.0.20348.5622, 2025 10.0.26100.33438

• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2026-69521

• Multiple vulnerabilities in Microsoft Windows