Out-of-bounds read in Microsoft Windows and Windows Server - CVE-2026-77491

Vulnerability identifier: #VU148172

CSH Severity: Low

CVSS v4: 4.6 [CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-77491

CWE-ID: CWE-125

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to disclose information.

The vulnerability exists due to an out-of-bounds read in Windows GDI when processing local operations requiring user interaction. A remote attacker can trigger the out-of-bounds read to disclose information.

Successful exploitation could expose small portions of heap memory.

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 6.3.9600.23397, 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-2026-77491

• Multiple vulnerabilities in Microsoft Windows