CVE Alert: CVE-2025-53805 – Microsoft – Windows Server 2022

Risk verdict

High severity DoS risk from a network-accessible HTTP.sys flaw; no exploitation activity is evidenced at present, but remote triggering could disrupt services if unpatched.

Why this matters

Unauthenticated remote access can trigger an out-of-bounds read, potentially crashing web services and IIS-dependent apps. For organisations hosting public or hybrid web workloads, outages translate to downtime, SLA penalties, and reputational impact, especially where HTTP.sys is exposed.

Most likely attack path

An attacker sends crafted network traffic to a vulnerable Windows host running affected IIS/HTTP.sys. No user interaction or prior privileges are required; exploitation would cause a denial of service on the target host, with limited or no lateral movement beyond the compromised server until remediation.

Who is most exposed

Entities running Windows Server 2022/2025 or Windows 11 variants with IIS/public web endpoints are at risk, particularly where servers are reachable from the internet or shared networks. Typical exposure includes on-premise data centres and cloud-hosted VMs hosting web services.

Detection ideas

• Spikes in CPU/memory usage or crashes for HTTP.sys/IIS processes.
• Crash dumps and Event Viewer entries referencing HTTP.sys or out-of-bounds reads.
• Sudden increases in 503 errors or service restarts of webfront-end services.
• Unusual inbound traffic to port 80/443 without corresponding legitimate activity.
• Patch state showing systems unpatched against the CVE.

Mitigation and prioritisation

• Apply the latest Microsoft security updates to affected OS versions; verify patch level across all servers.
• Restrict external access to HTTP.sys/endpoints via firewalls or API gateways; enable least-privilege exposure.
• Enable enhanced logging and crash-dump collection for rapid triage; test in a staging environment before broad rollout.
• Implement a short-change-change window for patching with fallback to validated restore points if issues arise.
• If KEV/EPSS indicators were present, escalate accordingly; with current data, treat as a high-priority mitigation task but not necessarily Priority 1.