Deserialization of Untrusted Data in Microsoft products - CVE-2026-83520

Vulnerability identifier: #VU154754

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-2026-83520

CWE-ID: CWE-502

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 deserialization of untrusted data in .NET when processing data from a specially crafted file. A remote attacker can trick a user into opening the crafted file to execute arbitrary code.

.NET
Visual Studio
Microsoft .NET Framework

Install security update from vendor's website.

.NET - addressed in versions 8.0.32, 9.0.21
Visual Studio - update to 17.14.42
Microsoft .NET Framework - addressed in versions 2.0.50727.8987 AND 3.0.30729.8982, 2.0.50727.8987 AND 3.0.30729.8982 AND 4.7.4150.0, 2.0.50727.9073 AND 3.0.30729.9070 AND 4.8.4811.0, 2.0.50727.9188 AND 3.0.30729.9171 AND 4.8.4811.0, 2.0.50727.9188 AND 3.0.30729.9171 AND 4.8.9363.0, 4.7.4150.0, 4.8.4811.0, 10.0.13

• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2026-83520
• https://support.microsoft.com/help/5130036

• Multiple vulnerabilities in Microsoft Windows