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CVE-2026-88099 Microsoft CVE debrief

AI-assisted PatchSiren debrief based on the supplied source corpus. The CVE record was published on 2026-10-13T19:00:20.593Z and has not been modified since then. This medium-severity vulnerability in Windows Failover Cluster could allow an unauthorized attacker to deny service over a network, affecting Windows Server 2019, 2022, and 2025, including Server Core installations. Defenders should prioritize verifying exposure, applying patches, and monitoring cluster configurations. The CVE record and source item provide details on the vulnerability, but specific details on exploitation or impact are limited.

Vendor
Microsoft
Product
Windows Server 2019
CVSS
MEDIUM 5.9
CISA KEV
Not listed in stored evidence
Original CVE published
2026-10-13
Original CVE updated
2026-10-13
Advisory published
2026-10-13
Advisory updated
2026-10-13

Who should care

Defenders responsible for Windows Server deployments, especially those using Failover Cluster configurations in Windows Server 2019, 2022, and 2025, should assess exposure and prioritize patching or mitigation.

Why it matters

CVE-2026-88099 is a medium-severity vulnerability in Windows Failover Cluster that could allow an unauthorized attacker to deny service. Defenders should prioritize verifying exposure, applying patches, and monitoring cluster configurations.

  • Potential denial-of-service impact on Windows Failover Cluster configurations.
  • Need to verify exposure and apply patches or updates.
  • Importance of monitoring cluster configurations for unusual activity.
  • Potential impact on incident response plans for denial-of-service scenarios.

Technical summary

The CVE record describes a vulnerability in Windows Failover Cluster that could allow an unauthorized attacker to deny service over a network. The vulnerability affects Windows Server 2019, 2022, and 2025, including Server Core installations. This vulnerability is a medium-severity issue, with a CVSS score of 5.9 and a CVSS severity of MEDIUM. The vulnerability is caused by an uncaught exception in Windows Failover Cluster.

Defensive priority

Defenders should prioritize verifying exposure in Windows Server 2019, 2022, and 2025 deployments, especially those using Failover Cluster configurations.

Recommended defensive actions

  • Verify exposure in Windows Server 2019, 2022, and 2025 deployments using Failover Cluster configurations.
  • Check for and apply vendor-provided patches or updates.
  • Monitor cluster configurations for unusual activity or service disruptions.
  • Review and update incident response plans to address potential denial-of-service scenarios.

Evidence notes

The CVE record and source item provide details on the vulnerability in Windows Failover Cluster, but specific details on exploitation or impact are limited.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-88099 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-88099

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-88099 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-88099

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Windows Failover Cluster Denial of Service Vulnerability

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/88xxx/CVE-2026-88099.json

    cve_program_cvelist_v5

  • Source reference

    Unverified legacy reference

    URL: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-88099

    Supplemental source - vendor-advisory, patch

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.