Microsoft’s advisory for a newly referenced HTTP.sys vulnerability describes an out‑of‑bounds read in the Windows HTTP protocol stack that can be triggered remotely against Internet Information Services (IIS) and other HTTP.sys consumers, allowing an unauthenticated attacker to cause a denial‑of‑service over the network — however, the CVE identifier provided (CVE‑2025‑53805) could not be located in major public trackers at the time of reporting and should be treated with caution until vendor pages and NVD records are synchronized.
HTTP.sys is the kernel‑mode HTTP protocol stack used by Windows to accept and route HTTP requests. Because it runs in kernel context and services platform‑level handlers used by IIS, application servers and numerous Microsoft components, vulnerabilities in HTTP.sys can have outsized operational impact — typically forcing crashes or resource exhaustion that ripple through the host and its dependent services. The class of bug now reported — an out‑of‑bounds read (CWE‑125) — is particularly concerning for kernel modules because it can lead to process crashes, uncontrolled resource consumption, or (in rare chains) information disclosure that helps later stages of an attack. Independent reporting has repeatedly documented similar HTTP.sys denial‑of‑service issues in recent years, confirming the recurring targeting of this component. (app.opencve.io)
Background
HTTP.sys is the kernel‑mode HTTP protocol stack used by Windows to accept and route HTTP requests. Because it runs in kernel context and services platform‑level handlers used by IIS, application servers and numerous Microsoft components, vulnerabilities in HTTP.sys can have outsized operational impact — typically forcing crashes or resource exhaustion that ripple through the host and its dependent services. The class of bug now reported — an out‑of‑bounds read (CWE‑125) — is particularly concerning for kernel modules because it can lead to process crashes, uncontrolled resource consumption, or (in rare chains) information disclosure that helps later stages of an attack. Independent reporting has repeatedly documented similar HTTP.sys denial‑of‑service issues in recent years, confirming the recurring targeting of this component. (app.opencve.io)What the advisory claims (summary)
- A vulnerability exists in HTTP.sys that permits a remote, unauthenticated attacker to trigger an out‑of‑bounds read, destabilize the HTTP.sys process, and cause a denial‑of‑service condition over the network.
- The behavior is network‑facing: attackers can exploit reachable HTTP endpoints (IIS sites, services that rely on HTTP.sys, or any binding that uses the kernel HTTP stack).
- Microsoft’s internal record page for the CVE is reachable but rendered via a dynamic web app; some details are present only in the MSRC update guide and related KBs. Because the MSRC page required JavaScript to render, external aggregators and NVD entries were used to cross‑check technical descriptors and mitigation guidance. (msrc.microsoft.com, app.opencve.io, cvedetails.com, app.opencve.io, app.opencve.io, rapid7.com, app.opencve.io, app.opencve.io, cvedetails.com)
- Internal community analysis and forum discussions emphasize practical mitigations (isolate internet‑facing hosts, monitor for probes, rotate remediation in prioritized windows) and provide operational context for administrators handling Windows servers in heterogeneous estate environments.
