Microsoft Windows: Remote code execution in RPC Runtime Library
Summary
The Windows RPC Runtime Library contains an out-of-bounds write (CWE-787) that allows remote code execution. Per the CVE record, an unauthenticated attacker with network access can run code without user interaction. CVSS 3.1 is 9.8 (Critical).
Affected
- Windows 10 Version 1607 (builds below 10.0.14393.9612)
- Windows 10 Version 1809 (builds below 10.0.17763.9376)
- Windows 10 Version 21H2 (builds below 10.0.19044.7807)
- Windows 10 Version 22H2 (builds below 10.0.19045.7807)
- Windows 11 Version 23H2 (builds below 10.0.22631.7652)
- Windows 11 Version 24H2, 25H2, 26H1 and 26H2 (see MSRC for exact builds)
- Windows Server 2012 and 2012 R2, including Server Core (see MSRC for exact builds)
- Windows Server 2016 (builds below 10.0.14393.9612)
Fixed in
- Windows 10 Version 1607: 10.0.14393.9612 or later (consistent across the sources reviewed)
- Other versions: install the October 2026 cumulative update. The fixed build numbers in the sources conflict for some versions, so verify them in the MSRC Security Update Guide.
Workaround
Unknown.
Exploitation
- CISA SSVC: exploitation none, automatable yes, technical impact total.
- No confirmed active exploitation is documented in the sources reviewed.
Our recommendation
- Identify all Windows systems and servers in scope, including Windows 10 1607 and Windows Server 2012 to 2016.
- Install the October 2026 cumulative update on every affected system and verify the build number against the MSRC Security Update Guide.
- Restrict network access to RPC services where possible and monitor for unusual RPC traffic and unexpected process activity.
- Prioritise internet-facing and domain-critical systems.
Information from Microsoft (Patch Tuesday October 2026)
- Severity (Microsoft)
- Important
- Impact
- Remote code execution – RPC Runtime
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation less likely
- Product family
- Windows, Windows ESU (Extended Security Updates)
- Updates (KB)
- KB5127648, KB5126651, KB5126655, KB5126657, KB5126646, KB5126653
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-83910 msrc.microsoft.com
- ZDI October 2026 security update review www.zerodayinitiative.com
- OffSeq threat radar: CVE-2026-83910 radar.offseq.com
- OpenCVE: CVE-2026-83910 app.opencve.io
- Vulners NVD mirror: CVE-2026-83910 vulners.com
- Strix: CVE-2026-83910 www.strix.ai
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 30 Oct 2026, 18:32.
Original description (NVD)
Out-of-bounds write in RPC Runtime allows an unauthorized attacker to execute code over a network.
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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