# CVE-2026-83666: Microsoft Active Directory Certificate Services race condition

Source: https://junglewise.ai/threats/cve-2026-83666-concurrent-execution-using-shared-resource-with-improper  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-13. Updated: 2026-10-29  
License: CC BY 4.0 with a link back

CVE-2026-83666 · Severity: high · CVSS 7 · Published 2026-10-13

Active Directory Certificate Services (AD CS) is a Microsoft service that manages digital certificates used to authenticate users and devices in enterprise networks. A race condition vulnerability allows an authorized attacker with local access to elevate their privileges on affected systems, potentially gaining administrative control and compromising the entire certificate infrastructure.

Technologies: [Microsoft Active Directory Certificate Services](https://junglewise.ai/threats/technologies/active-directory-certificate-services), [Microsoft Windows 10 1607](https://junglewise.ai/threats/technologies/windows-10-1607), [Microsoft Windows 10 1809](https://junglewise.ai/threats/technologies/windows-10-1809), [Microsoft Windows Server 2012](https://junglewise.ai/threats/technologies/windows-server-2012), [Microsoft Windows Server 2016](https://junglewise.ai/threats/technologies/windows-server-2016), [Microsoft Windows Server 2019](https://junglewise.ai/threats/technologies/windows-server-2019), [Microsoft Windows Server 2022](https://junglewise.ai/threats/technologies/windows-server-2022), [Microsoft Windows Server 2025](https://junglewise.ai/threats/technologies/windows-server-2025). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2026-83666 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-83666 being exploited in the wild.

**How severe is CVE-2026-83666?** High severity, with a CVSS score of 7, published 13 October 2026.

**Which products and versions are affected?** Microsoft Active Directory Certificate Services.

**Is there a fix for CVE-2026-83666?** 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-2026-83666 attacked?** It is attacked with local access.

**Am I affected by CVE-2026-83666?** Check whether you run Microsoft Active Directory Certificate Services, Microsoft Windows 10 1607, Microsoft Windows 10 1809 or one of the others listed. 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 race condition in concurrent execution using shared resources with improper synchronization affects Active Directory Certificate Services. An authenticated local attacker can exploit this to escalate privileges; the vulnerability requires local access and valid credentials. A fix from Microsoft is referenced in the update guide.

## Affected products

- Microsoft Active Directory Certificate Services

## Timeline

- 2026-10-13: disclosed

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-83666](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-83666)

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