Microsoft Windows NPS: Heap-based buffer overflow enables remote code execution
Summary
Network Policy Server (NPS) in affected Windows 10, Windows 11 and Windows Server versions contains a heap-based buffer overflow. An unauthenticated attacker on the network can exploit it to execute code. Microsoft rates the flaw critical (CVSS 9.8), and CISA's SSVC assessment reports no known exploitation and not automatable.
Affected
- Windows 10 Version 1607 (10.0.14393.0 before 10.0.14393.9612)
- Windows 10 Version 1809 (10.0.17763.0 before 10.0.17763.9376)
- Windows 10 Version 21H2 (10.0.19044.0 before 10.0.19044.7807)
- Windows 10 Version 22H2 (10.0.19045.0 before 10.0.19045.7807)
- Windows 11 Version 23H2 (10.0.22631.0 before 10.0.22631.7652)
- Windows 11 Version 24H2 (10.0.26100.0 before 10.0.26100.9711)
- Windows 11 Version 25H2 (10.0.26200.0 before 10.0.26200.9711)
- Windows 11 Version 26H1 (10.0.28000.0 before 10.0.28000.3231)
- Windows 11 Version 26H2 (10.0.26300.0 before 10.0.26300.9711)
- Windows Server 2012 and Server Core installation (6.2.9200.0 before 6.2.9200.26434)
- Windows Server 2012 R2 and Server Core installation (6.3.9600.0 before 6.3.9600.23470)
- Windows Server 2016 (10.0.14393.0 before 10.0.14393.9612)
Fixed in
Install the Microsoft security update that brings the systems to the build numbers listed above or later. Exact KB numbers: Unknown (see MSRC).
Workaround
Unknown.
Exploitation
- CISA SSVC: exploitation none, not automatable, total technical impact.
- No public exploitation reported at the time of the analysis.
Our recommendation
- Install the October 2026 Microsoft security update on all affected systems, prioritising servers running the NPS role.
- Verify whether NPS (RADIUS) is in use; if not, disable the role.
- Restrict network access to NPS/RADIUS ports to known clients only.
- Monitor NPS servers for unusual crashes or unexpected process execution.
Information from Microsoft (Patch Tuesday October 2026)
- Severity (Microsoft)
- Important
- Impact
- Remote code execution – Network Policy Server (NPS)
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation less likely
- Product family
- Windows, Windows ESU (Extended Security Updates)
- Updates (KB)
- KB5126835, KB5126836, KB5126868, KB5126651, KB5126657, KB5126655
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-100222 msrc.microsoft.com
- NVD entry via Vulners vulners.com
- CVE monitoring (Intruder) cvemon.intruder.io
- Senserva Patch Tuesday October 2026 senserva.com
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, 18:58.
Original description (NVD)
Heap-based buffer overflow in Network Policy Server (NPS) 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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