Windows Management Instrumentation: Elevation of privilege via deserialization
Summary
A local user with low privileges can exploit a deserialization flaw in Windows Management Instrumentation (WMI) to gain higher privileges, up to SYSTEM. The CVE covers many Windows 10, Windows 11 and Windows Server builds, including Windows 10 Version 1607. The CVSS 3.1 base score is 7.8, and the attack requires a local foothold such as a standard user account or malware. Microsoft reports the vulnerability as not publicly disclosed and not exploited.
Affected
- Windows 10 Version 1607 (Enterprise LTSB 2016): 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: 10.0.26100.0 to < 10.0.26100.9711
- 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 (incl. Server Core): 6.2.9200.0 to < 6.2.9200.26434
- Windows Server 2012 R2 (incl. 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
- Windows 10 Version 1607: build 10.0.14393.9612 (KB5126868, according to Microsoft release health)
- Windows 10 Version 1809: build 10.0.17763.9376
- Windows 10 Version 21H2: build 10.0.19044.7807
- Windows 10 Version 22H2: build 10.0.19045.7807
- Windows 11 Version 23H2: build 10.0.22631.7652
- Windows 11 Version 24H2: build 10.0.26100.9711
- Windows 11 Version 25H2: build 10.0.26200.9711
- Windows 11 Version 26H1: build 10.0.28000.3231
- Windows 11 Version 26H2: build 10.0.26300.9711
- Windows Server 2012: build 6.2.9200.26434
- Windows Server 2012 R2: build 6.3.9600.23470
- Windows Server 2016: build 10.0.14393.9612
- Patch for Windows 10 Version 1607 is only confirmed for the listed build; whether ESU covers this CVE is unknown.
Workaround
Unknown. Microsoft has not confirmed a workaround for this CVE. As general practice for local privilege escalation, restrict local logons, remove unnecessary administrator rights, enforce application allowlisting and isolate legacy devices from the network.
Exploitation
- Microsoft: not publicly disclosed, not exploited.
- CISA SSVC assessment: exploitation none, not automatable, total technical impact.
- No public proof of concept or CISA KEV entry was found in the research. Absence of evidence is not proof that none exists.
- VulDB estimates an exploit market price of about USD 5k to 25k, which is not evidence of a working exploit.
Our recommendation
- Apply the October 2026 cumulative update for the Windows build in use, matching the build numbers in the MSRC table.
- Prioritise Windows 10 Version 1607 (LTSB 2016) devices such as kiosks, POS, HMI and thin clients. Microsoft reports end of extended support on 13 Oct 2026. Confirm with Microsoft whether ESU is required and plan migration, for example to Windows 11 Enterprise LTSC 2024.
- Until patched, limit local accounts and admin rights, and isolate unpatched legacy devices.
- Monitor for unusual privilege changes and WMI activity on endpoints.
- Verify the MSRC advisory before publishing mitigations as official.
Information from Microsoft (Patch Tuesday October 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Windows Management Instrumentation
- 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
- MSRC Security Update Guide: CVE-2026-88091 msrc.microsoft.com
- Microsoft Learn: Windows 10 1607 and Windows Server 2016 release health learn.microsoft.com
- 4sysops: Windows 10 LTSB 2016 end of support and ESU 4sysops.com
- Vulners: MS:CVE-2026-88091 vulners.com
- OffSeq Radar: CVE-2026-88091 radar.offseq.com
- VulDB: CVE-2026-88091 vuldb.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 2 Nov 2026, 01:30.
Original description (NVD)
Deserialization of untrusted data in Windows Management Instrumentation allows an authorized attacker to elevate privileges locally.
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.
Affected? We can help.
We check whether your systems are affected, install updates and close the gap – continuously with the System Health Checker if you wish.