# CVE-2026-71338: Microsoft Windows Failover Cluster double free privilege escalation

Source: https://junglewise.ai/threats/cve-2026-71338-microsoft-windows-failover-cluster-double-free-privilege  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-08. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-71338 · Severity: medium · CVSS 6.4 · Published 2026-09-08

Windows Failover Cluster is a Microsoft system component that manages clusters of servers for high availability. A double-free memory vulnerability allows an authorized local user to escalate their privileges on the system, potentially gaining administrative access without proper authorization.

Technologies: [Microsoft Windows Failover Cluster](https://junglewise.ai/threats/technologies/windows-failover-cluster). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2026-71338 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-71338 being exploited in the wild.

**How severe is CVE-2026-71338?** Medium severity, with a CVSS score of 6.4, published 8 September 2026.

**Which products and versions are affected?** Microsoft Windows Failover Cluster <UNKNOWN>.

**Is there a fix for CVE-2026-71338?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-71338 attacked?** It is attacked with local access, in an operating system.

**Am I affected by CVE-2026-71338?** Check whether you run Microsoft Windows Failover Cluster at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A double-free vulnerability exists in Windows Failover Cluster where memory is freed twice in certain code paths, potentially leading to heap corruption and code execution. The vulnerability requires prior authentication/authorization to trigger, as it can only be exploited by an authorized local attacker with existing access to the system. The attack vector is local; it does not require network access. Successful exploitation allows privilege escalation from the attacker's current user context to a higher privilege level. Microsoft has issued a security patch to resolve this issue.

## Affected products

- Microsoft Windows Failover Cluster <UNKNOWN>

## Timeline

- 2026-09-08: disclosed

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-71338](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-71338)

## Related threats

- [Windows Failover Cluster use after free privilege escalation](https://junglewise.ai/threats/cve-2026-119869-use-after-free-in-windows-failover-cluster-allows-an-authorized)
- [Microsoft Windows Failover Cluster denial of service via uncaught exception](https://junglewise.ai/threats/cve-2026-96945-uncaught-exception-in-windows-failover-cluster-allows-an)
- [Microsoft Windows Failover Cluster use-after-free](https://junglewise.ai/threats/cve-2026-88102-use-after-free-in-windows-failover-cluster-allows-an-unauthorized)
- [Windows Failover Cluster uncaught exception denial of service](https://junglewise.ai/threats/cve-2026-88099-uncaught-exception-in-windows-failover-cluster-allows-an)
- [Windows Failover Cluster integer underflow denial of service](https://junglewise.ai/threats/cve-2026-102192-integer-underflow-wrap-or-wraparound-in-windows-failover-cluster)