Advisory · CVE-2026-102203
Type confusion in Windows RPC Runtime can run code
The Windows RPC Runtime has a type confusion flaw a remote attacker can use to execute code when a victim interacts. Microsoft rates it CVSS 3.1 8.8.
- Vendor
- Microsoft
- Product
- Windows RPC Runtime
- Identifier / CWE
- CVE-2026-102203
CWE-843 - Action timing
- Immediate
Explain it like I’m five
RPC is the plumbing between Windows components; a type confusion there means the plumbing can be made to run the wrong thing entirely.
- 01Attacker engages the component
A remote or authorized attacker sends crafted content or requests to Windows RPC Runtime.
- 02Weakness triggers
The component mishandles the input and the flaw takes effect.
- 03Impact lands
The attacker gains the execution, elevation, or access the flaw allows.
What happened
Microsoft disclosed CVE-2026-102203 in its October 2026 update guide: a type confusion weakness (CWE-843) in the Windows RPC Runtime lets a remote attacker execute code, with user interaction in Microsoft’s scenario.
Microsoft lists the affected releases and their patched build thresholds in its update guide. Apply the October 2026 security updates for your release rather than relying on a version guess here.
What to do
- Inventory every Windows RPC Runtime deployment, including test, training, and individually managed instances.
- Apply the vendor fix or upgrade exactly as directed in the linked vendor bulletin or advisory.
- Restrict network access to Windows RPC Runtime while remediation is underway, especially for internet-facing instances.
- Review application and server logs for RPC service crashes and unusual inter-process communication errors after content arrives.
- Check for accounts, content, or configuration created outside normal change processes, and rotate exposed credentials where access cannot be ruled out.
- Verify the deployed version or patch level after remediation.
Management note
Core plumbing flaws deserve fleet-wide treatment. Apply the October updates on the normal urgent ring.