Verify Windows RPC Patches Now to Block High-Severity Remote Code Execution Flaw

An attacker can execute arbitrary code on a remote Windows system by exploiting a type confusion flaw in the RPC Runtime component, according to the Microsoft Security Update Guide. This vulnerability, identified as CVE-2026-102203, allows an unauthorized attacker to execute code over a network.

The National Vulnerability Database assigns a CVSS score of 8.8 to this issue, classifying it as high severity. The weakness stems from how the RPC Runtime handles resource access using incompatible data types. This type confusion allows an attacker to execute code remotely, potentially compromising the system.

Context and background

Microsoft released this advisory to address a gap in the RPC Runtime infrastructure. The flaw exists in how the component processes certain data types during network communications. This specific mechanism allows an unauthorized attacker to execute code. The issue involves access of resource using incompatible type, as described in the official advisory.

Affected systems

Microsoft Windows 10 Version 1607 remains vulnerable if the build number is below 10.0.14393.9612. Windows 10 Version 1809 is affected until build 10.0.17763.9376 is installed. Users of Windows 10 Version 21H2 and 22H2 must update to build 10.0.19044.7807 or later. Windows 11 version 23H2 requires build 10.0.22631.7652 to mitigate this risk.

What to watch

Administrators should verify current build numbers against the list provided by Microsoft. Check system logs for unusual RPC activity or unexpected network connections. Monitor for any new advisories regarding this CVE. Ensure that patch management processes are functioning correctly to deploy updates promptly. Watch for signs of lateral movement if a system is suspected to be compromised.

What made it possible

Type confusion vulnerabilities occur when software misinterprets the data type of an object. Attackers exploit this by sending crafted data that the system processes incorrectly. This often happens during network protocol handling. Such flaws serve as an initial access vector, allowing remote attackers to gain control. Teams usually monitor for anomalous data structures in network traffic. Checking input validation routines can help identify similar weaknesses before they are exploited.

Background: Lateral movement

Lateral movement is the process where an attacker navigates through a network after initial access. They move from one system to another to reach high-value targets. This tactic exploits trust relationships and weak internal controls. Understanding this meaning helps you secure internal pathways, not just the outer gate.

Read the full guide: Lateral Movement Meaning: How Attackers Spread Inside Your Network

What to do and how to stay safe: Microsoft

• Audit your Windows 10 and 11 systems to identify current build numbers.
• Compare your build numbers against the vulnerable versions listed by Microsoft.
• Apply the latest cumulative updates to ensure you are on a patched build.
• Restrict network access to RPC services where possible to reduce exposure.

Step-by-step guide: How Security Advisories Drive Patch Decisions and Reduce Risk

General security guidance from the Shell Bulletin newsroom. It is not confirmed advice from the organisations named in this story.

Frequently asked questions

What is CVE-2026-102203?

It is a remote code execution vulnerability in Microsoft RPC Runtime caused by a type confusion flaw.

Which Windows versions are affected?

Windows 10 versions 1607, 1809, 21H2, 22H2 and Windows 11 version 23H2 are affected if not updated.

Is this vulnerability rated critical?

No, the NVD rates it as high severity with a CVSS score of 8.8.