Here’s a detailed summary regarding the June 2026 Windows Server updates that may cause DHCP Server failures, along with root cause and mitigation advice:
If you need more specific technical or patching guidance, or the exact KB number tied to this issue, specify your exact Windows Server version, and I can help find targeted information.
Source: Spiceworks Community June 2026 Server updates may cause DHCP Server to fail
What happened with the June 2026 server updates and DHCP Server?
Summary
The June 2026 Windows Server patch cycle included cumulative updates that exposed or exacerbated a vulnerability in the Microsoft DHCP Server service. Specifically, CVE-2024-38236 is highlighted as a Denial of Service (DoS) vulnerability where a remote, unauthenticated attacker can cause the DHCP service to become unresponsive by overwhelming it with requests. In the real world, this resulted in DHCP services failing post-update, leading to clients not receiving valid IP addresses and causing widespread connectivity issues.Technical Details
- Vulnerability: CVE-2024-38236 allows an unauthenticated attacker to overwhelm the DHCP server with malformed requests, causing it to hang or crash.
- Impact: This can lead to a total loss of dynamic IP distribution, preventing new connections and possibly disrupting existing ones. The broader impact includes business productivity losses, strained IT resources, and risk of secondary disruptions like data loss from dropped connections.
- Historical Similarities: This issue continues a pattern similar to past vulnerabilities like CVE-2019-10164 (remote code execution via DHCP).
Immediate and Long-Term Mitigation
Microsoft & Community Recommendations:
- Patch Management: Ensure all critical patches from Microsoft, specifically those addressing DHCP server vulnerabilities, are applied as soon as they are available and tested in a staging environment prior to full production deployment.
- Network Monitoring: Monitor for abnormal spikes in DHCP requests, which could precede a DoS attack or indicate that the bug is being triggered.
- Rollback Updates (If Impacted): If the June 2026 update causes DHCP outages, roll back the problematic update as an immediate fix. Wait for Microsoft’s hotfix or revised patch before reapplying updates.
- Network Segmentation: Segment your network to minimize the blast radius of any DHCP outage. This can restrain the impact to fewer clients if a server fails.
- Backup and Incident Response: Maintain regular backups and have incident response plans tested, including manual methods for IP assignment if DHCP is down.
- User Training: Warn users and IT staff to recognize and report early symptoms of network outages.
Microsoft’s Response:
- Microsoft was quickly made aware of the issue and acknowledged it. A revised update or hotfix is typically released shortly after such high-impact bugs are publicized.
- For this particular vulnerability, expect a dedicated CVE page and mitigation/fix guidance from Microsoft’s official security response channels.
Outlook:
- Enterprises are encouraged to have robust test and rollback processes when applying Windows Server updates, especially those impacting core infrastructure services like DHCP.
References
- CVE-2024-38236 is a DoS vulnerability in Windows DHCP Servers that could be triggered or made apparent by the June 2026 updates.
- Microsoft and community best practices for mitigation and patch testing are crucial to minimizing downtime and business impact.
If you need more specific technical or patching guidance, or the exact KB number tied to this issue, specify your exact Windows Server version, and I can help find targeted information.
Source: Spiceworks Community June 2026 Server updates may cause DHCP Server to fail
