# CVE-2026-77889: Microsoft Windows DHCP Server type confusion denial of service

Source: https://junglewise.ai/threats/cve-2026-77889-microsoft-windows-dhcp-server-type-confusion-denial-of-service  
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-2026-77889 · Severity: high · CVSS 7.5 · Published 2026-09-08

Windows DHCP Server is a network service that assigns IP addresses to devices on corporate networks. A type confusion vulnerability allows an unauthenticated attacker to crash the DHCP service over the network, disrupting IP address allocation and potentially rendering network connectivity unavailable for affected devices.

Technologies: [Microsoft Windows DHCP Server](https://junglewise.ai/threats/technologies/windows-dhcp-server). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2026-77889 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-77889 being exploited in the wild.

**How severe is CVE-2026-77889?** High severity, with a CVSS score of 7.5, published 8 September 2026.

**Which products and versions are affected?** Microsoft Windows DHCP Server multiple versions.

**Is there a fix for CVE-2026-77889?** 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-2026-77889 attacked?** It is attacked over the network, in an operating system.

**Am I affected by CVE-2026-77889?** Check whether you run Microsoft Windows DHCP Server 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 type confusion vulnerability (CWE-843) in Windows DHCP Server allows an attacker to access memory resources using an incompatible type, triggering a denial of service condition. The vulnerability is network-reachable and requires no authentication or user interaction. An attacker can send a specially crafted DHCP message to crash the DHCP Server service, preventing legitimate clients from obtaining IP addresses. A patch is available from Microsoft.

## Affected products

- Microsoft Windows DHCP Server multiple versions

## Timeline

- 2026-09-08: disclosed

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-77889](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-77889)

## Related threats

- [Microsoft Windows DHCP Server uncontrolled resource consumption](https://junglewise.ai/threats/cve-2026-96134-uncontrolled-resource-consumption-in-windows-dhcp-server-allows)
- [Windows DHCP Server time-of-check time-of-use race condition](https://junglewise.ai/threats/cve-2026-88216-time-of-check-time-of-use-toctou-race-condition-in-windows-dhcp)
- [Microsoft Windows DHCP Server use-after-free remote code execution](https://junglewise.ai/threats/cve-2026-72998-use-after-free-in-windows-dhcp-server-allows-an-unauthorized)
- [Windows DHCP Server out-of-bounds read](https://junglewise.ai/threats/cve-2026-119890-out-of-bounds-read-in-windows-dhcp-server-allows-an-authorized)
- [Microsoft Windows DHCP Server improper access control](https://junglewise.ai/threats/cve-2026-113773-improper-access-control-in-windows-dhcp-server-allows-an)