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Windows Partition Management Driver: Heap-based buffer overflow

CVE-2026-83851High 8.8

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Summary

A heap-based buffer overflow in the Windows Partition Management Driver allows an attacker to elevate privileges. NVD scores it CVSS 3.1 8.8 with the vector AV:N/AC:L/PR:N/UI:R, so user interaction is required. The attack path has not been verified, and no exploitation in the wild is known.

Affected

  • Windows 10 Version 1809 and Windows Server 2019 (including Server Core): builds 10.0.17763.0 to before 10.0.17763.9376
  • Windows 10 Version 21H2: builds 10.0.19044.0 to before 10.0.19044.7807
  • Windows 10 Version 22H2: builds 10.0.19045.0 to before 10.0.19045.7807
  • Windows Server 2022: builds 10.0.20348.0 to before 10.0.20348.5761
  • Windows 11 23H2, 24H2, 25H2, 26H1 and 26H2 (see the MSRC advisory for exact builds)
  • Windows Server 2025 (including Server Core): builds 10.0.26100.0 to before 10.0.26100.33650

Fixed in

  • Windows 10 1809 and Windows Server 2019: build 10.0.17763.9376 (October 2026 cumulative update KB5126651)
  • Windows 10 21H2 and 22H2: build 10.0.19044.7807 and 10.0.19045.7807
  • Windows Server 2022: build 10.0.20348.5761
  • Windows Server 2025: build 10.0.26100.33650
  • Windows 11 and other branches: see the MSRC advisory
  • Out-of-band update KB5134124 (build 17763.9378) for 1809 is reported as newer, but its coverage of this CVE is not confirmed

Workaround

  • Unknown. No documented interim mitigation was found. Apply the security update.

Exploitation

  • CISA SSVC: exploitation none, automatable no, technical impact total
  • Not listed in the CISA KEV catalog
  • No public proof of concept found
  • VulDB estimates an exploit price of USD 25k to 100k; this is not evidence of actual use

Our recommendation

  • Inventory all Windows 10 1809 and Server 2019 hosts and check their build numbers. Treat builds below 17763.9376 as vulnerable.
  • Install the latest cumulative update for each affected branch and verify the fixed build on the MSRC advisory.
  • Test KB5126651 before broad rollout, because known issues with Endpoint Mapper memory limits and Exchange instability have been reported.
  • Check whether Windows 10 1809 is still supported for each system and plan upgrades where it is not.
  • Monitor the CISA KEV catalog and the MSRC page for changes in exploitation status.

Information from Microsoft (Patch Tuesday October 2026)

Severity (Microsoft)
Important
Impact
Elevation of privilege – Windows Partition Management Driver
Status on Patch Tuesday
Neither exploited nor publicly disclosed
Exploitability assessment
Exploitation unlikely
Product family
Windows, Windows ESU (Extended Security Updates)
Updates (KB)
KB5126651, KB5126655, KB5126657, KB5126646, KB5127648, 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 31 Oct 2026, 18:28.

Original description (NVD)

Heap-based buffer overflow in Windows Partition Management Driver allows an unauthorized attacker to elevate privileges over a network.

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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