Vulnerabilities
Windows DHCP Server Denial of Service Vulnerability (CVE‑2026‑77886) – Immediate Patch Required
Microsoft has disclosed a denial‑of‑service flaw in the Windows DHCP Server that can be triggered by a crafted request, potentially disrupting network services. The issue affects all Windows Server editions that run the DHCP service. Administrators should apply the latest cumulative update and verify service stability.
What Happened
Microsoft identified a flaw in the Windows DHCP Server that allows a remote attacker to send a specially crafted packet, causing the DHCP service to crash and resulting in a denial of service for all clients on the network.
Impact
All Windows Server editions that host the DHCP service are affected, including Server 2022, 2019, 2016, and earlier releases. The vulnerability can lead to a loss of IP address allocation and network connectivity for all devices relying on the compromised DHCP server.
What to Do
- Apply the latest cumulative update for Windows Server that contains the fix for CVE‑2026‑77886.
- Verify that the DHCP service is running correctly after the update by checking event logs for any crash reports.
- Consider temporarily disabling the DHCP service if it is not required for critical operations until the patch is applied.
- Monitor network traffic for unusual DHCP packets and review firewall rules to restrict DHCP traffic to trusted sources.
Additional Mitigation
Until the patch is applied, administrators can isolate the DHCP server on a separate VLAN and enforce strict access controls to limit exposure to potential attackers.
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