Microsoft Windows Server: Remote code execution in Failover Cluster
Summary
A use-after-free vulnerability (CWE-416) in the Windows Failover Cluster feature allows an unauthenticated attacker to execute code over the network. Microsoft rates the CVSS 3.1 base score as 9.8 (Critical), while its own maximum severity is Important. The risk applies only to servers where the Failover Cluster role is installed and reachable from untrusted networks.
Affected
- Windows Server 2019 and Server 2019 (Server Core): below 10.0.17763.9376
- Windows Server 2022: below 10.0.20348.5761
- Windows Server 2025 and Server 2025 (Server Core): below 10.0.26100.33650
- Windows 10 version 1809 and Windows Server 2016: Unknown, not listed in the sources reviewed
Fixed in
- Windows Server 2019 and Server 2019 (Server Core): build 10.0.17763.9376 or later
- Windows Server 2022: build 10.0.20348.5761 or later
- Windows Server 2025 and Server 2025 (Server Core): build 10.0.26100.33650 or later
- Security update released on 13 October 2026; KB numbers to be verified on the MSRC advisory
Workaround
Unknown. Microsoft's advisory mentions that workarounds or hotfixes may offer interim remediation; no specific workaround was found in the sources reviewed.
Exploitation
- Not listed in CISA KEV; EPSS score below 1%
- CISA SSVC: exploitation none, automatable yes, technical impact total
- Microsoft temporal vector E:U (exploit code maturity Unproven)
- No public proof of concept or in-the-wild exploitation found in the sources reviewed
Our recommendation
- Inventory all servers and check whether the Failover Cluster feature is installed (for example with Get-WindowsFeature)
- Install the October 2026 security update on all affected cluster nodes, verify the build number, and test failover afterward
- Check the MSRC advisory for workarounds and confirm KB numbers before deployment
- Restrict cluster communication to trusted hosts and never expose cluster nodes to the internet
- Monitor cluster nodes for crashes or unexpected service restarts
- Check whether related CVE-2026-73010 also requires patches
Information from Microsoft (Patch Tuesday October 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-88102 msrc.microsoft.com
- Vulners CNA record: CVE-2026-88102 vulners.com
- Vulners Microsoft record: MS:CVE-2026-88102 vulners.com
- OpenCVE: CVE-2026-88102 app.opencve.io
- Offseq Radar: CVE-2026-88102 radar.offseq.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, 18:24.
Original description (NVD)
Use after free in Windows Failover Cluster 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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