Use-after-free in Microsoft Windows and Windows Server - CVE-2026-88121

Vulnerability identifier: #VU155320

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-2026-88121

CWE-ID: CWE-416

Exploitation vector: Adjecent network

Exploit availability: No public exploit available

The vulnerability allows a remote user on the local network to execute arbitrary code.

The vulnerability exists due to use-after-free in Windows Background Intelligent Transfer Service (BITS) when handling network interactions. A remote user on the local network can exploit the use-after-free over the local network to execute arbitrary code.

Microsoft Windows
Windows Server

Install security update from vendor's website.

Microsoft Windows - addressed in versions 10 21H2 10.0.19044.7807, 10 1607 10.0.14393.9612, 10 1809 10.0.17763.9376, 11 23H2 10.0.22631.7652, 11 24H2 10.0.26100.9711, 11 25H2 10.0.26200.9711, 11 26H1 10.0.28000.3231
Windows Server - addressed in versions 2012 R2 6.3.9600.23470, 2012 6.2.9200.26434, 2016 10.0.14393.9612, 2019 10.0.17763.9376, 2022 10.0.20348.5761, 2025 10.0.26100.33650

• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2026-88121

• Multiple vulnerabilities in Microsoft Windows