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Microsoft Windows: Elevation of privilege in WebDAV

CVE-2026-88126High 7.8

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Summary

The WebDAV component of Microsoft Windows contains an untrusted pointer dereference (CWE-822). An authenticated local user can exploit it to elevate privileges. Successful exploitation can lead to high impact on confidentiality, integrity and availability. Microsoft fixed the issue in the October 2026 security updates.

Affected

  • Windows 10 Version 1607: 10.0.14393.0 to < 10.0.14393.9612
  • Windows 10 Version 1809: 10.0.17763.0 to < 10.0.17763.9376
  • Windows 10 Version 21H2: 10.0.19044.0 to < 10.0.19044.7807
  • Windows 10 Version 22H2: 10.0.19045.0 to < 10.0.19045.7807
  • Windows 11 Version 23H2: 10.0.22631.0 to < 10.0.22631.7652
  • Windows 11 Version 24H2 and Windows Server 2025: sources conflict (see fixed)
  • Windows 11 Version 25H2: 10.0.26200.0 to < 10.0.26200.9711
  • Windows 11 Version 26H1: 10.0.28000.0 to < 10.0.28000.3231
  • Windows 11 Version 26H2: 10.0.26300.0 to < 10.0.26300.9711
  • Windows Server 2012 (including Server Core): 6.2.9200.0 to < 6.2.9200.26434
  • Windows Server 2012 R2 (including Server Core): 6.3.9600.0 to < 6.3.9600.23470
  • Windows Server 2016: 10.0.14393.0 to < 10.0.14393.9612

Fixed in

  • Fixed in the October 2026 security updates for each affected version (see MSRC for the exact KB per product)
  • Windows 11 Version 24H2: 10.0.26100.9711 according to one source; another source lists 10.0.26100.33650 for Windows Server 2025. Unresolved conflict.
  • Windows 10 Version 22H2: unknown, sources are inconsistent
  • Windows Server 2012: 6.2.9200.26434 (unconfirmed)

Workaround

  • Install the October 2026 security update for each affected Windows version.
  • If WebDAV is not required, restricting or disabling it may reduce exposure. This is not confirmed as official Microsoft guidance; test first, because WebClient mapped drives may depend on it.

Exploitation

  • No exploitation in the wild known.
  • No public proof of concept found.
  • CISA SSVC: exploitation none, not automatable, total technical impact.
  • VulDB lists the entry as confirmed; the exploit price range is a market estimate only.
  • Not found in CISA KEV at the time of research.

Our recommendation

  • Patch all affected Windows systems with the October 2026 security updates, prioritising multi-user servers, terminal servers and file servers.
  • Verify the fixed build for each product on the MSRC Security Update Guide before rollout, especially for Windows 10 22H2 and Windows Server 2025.
  • Check whether WebDAV or WebClient is in use and review IIS WebDAV exposure separately.
  • Restrict local logon to necessary users and monitor for unusual privilege escalation on servers.

Information from Microsoft (Patch Tuesday October 2026)

Severity (Microsoft)
Important
Impact
Elevation of privilege – WebDAV
Status on Patch Tuesday
Neither exploited nor publicly disclosed
Exploitability assessment
Exploitation less likely
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 2 Nov 2026, 01:22.

Original description (NVD)

Untrusted pointer dereference in WebDAV allows an authorized attacker to elevate privileges 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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