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Windows Network File System: Heap-based buffer overflow allows local code execution

CVE-2026-70143High 7.8

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Summary

A heap-based buffer overflow in the Windows Network File System (NFS) component allows an authorized attacker to execute code locally. The attacker needs a local account with low privileges and no user interaction, and the NVD/CVSS data (AV:L, CVSS 7.8) rates the impact on confidentiality, integrity and availability as high. The Microsoft CNA title refers to Remote Code Execution, so the attack vector should be confirmed against the MSRC advisory.

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 (builds below 10.0.26100.9711)
  • Windows 11 Version 25H2 (builds below 10.0.26200.9711)
  • Windows 11 Version 26H1 (builds below 10.0.28000.3231)
  • Windows 11 Version 26H2 (builds below 10.0.26300.9711)
  • Windows Server 2012 and Server Core installation (builds below 6.2.9200.26434)
  • Windows Server 2012 R2 and Server Core installation (builds below 6.3.9600.23470)
  • Windows Server 2016 (builds below 10.0.14393.9612)

Fixed in

  • Fixed builds per CNA data: see the affected builds above (first fixed build of each product line).
  • Windows 10 22H2: the fixed build is unverified because a source contains a typo.
  • KB numbers: Unknown for Windows 10 1607 and Server 2016. Tenable listed KB5126651 for Windows 10 1809/Server 2019 and KB5126646 for Server 2025.
  • Confirm all builds and KB numbers in the MSRC advisory.

Workaround

Unknown.

Exploitation

  • No evidence of exploitation in the wild found.
  • CISA SSVC: Exploitation none, Automatable no.
  • No public proof-of-concept found.
  • EPSS 0.00341 (low predicted exploitation probability).

Our recommendation

  • Install the Microsoft security update for each affected system, prioritizing Windows 10 1607 and Server 2016 hosts with NFS in use.
  • Patch terminal servers, file servers and jump hosts first, because a compromised user account there is the main risk.
  • Check whether Windows 10 1607 is still supported under Microsoft's lifecycle policy.
  • Restrict local logon to affected hosts to trusted users only.
  • Disable the NFS server or client features where they are not needed.
  • Monitor for unusual local privilege escalation and recheck CISA KEV and public PoCs in the coming days.

Information from Microsoft (Patch Tuesday October 2026)

Severity (Microsoft)
Important
Impact
Remote code execution – Windows Network File System
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

Entry in the Microsoft Security Update Guide

Public exploits

PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.

Research sources

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 2 Nov 2026, 04:05.

Original description (NVD)

Heap-based buffer overflow in Windows Network File System allows an authorized attacker to execute code locally.

NVD references (1)

Sources

The tracker combines official, freely usable data sources – updated continuously:

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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