CVE-2026-69597: Windows HTTP.sys Use After Free Vulnerability

CVE-2026-69597 Overview

CVE-2026-69597 is a use-after-free vulnerability [CWE-416] in the Windows HTTP protocol stack (HTTP.sys). An authorized attacker can exploit the flaw over a network to elevate privileges on an affected Windows system. Successful exploitation requires user interaction and high attack complexity, but yields high impact to confidentiality, integrity, and availability. Microsoft published the advisory on September 8, 2026, and the vulnerability is tracked under the CWE-416 memory safety category. No public proof-of-concept, exploit-in-the-wild activity, or CISA KEV listing has been reported at the time of publication.

Critical Impact
Successful exploitation permits privilege escalation against the Windows HTTP kernel driver, granting an authenticated attacker elevated rights across confidentiality, integrity, and availability.

Affected Products

Microsoft Windows (versions leveraging HTTP.sys) — refer to the Microsoft advisory for the definitive list
Windows Server roles that host HTTP-based services through HTTP.sys
IIS-hosted and WinRM-hosted services that rely on the Windows HTTP stack

Discovery Timeline

2026-09-08 - CVE-2026-69597 published to NVD
2026-09-09 - Last updated in NVD database

Technical Details for CVE-2026-69597

Vulnerability Analysis

The vulnerability resides in HTTP.sys, the Windows kernel-mode driver that services HTTP requests for IIS, WinRM, WSDAPI, and other components. A use-after-free condition [CWE-416] occurs when the driver references a memory object after it has been freed. An authorized attacker who can reach the HTTP endpoint and induce specific user interaction can drive the flawed code path. Exploitation escalates the attacker's privileges within the kernel context, exposing confidentiality, integrity, and availability of the target host.

Because HTTP.sys operates in kernel mode, any memory corruption in the driver carries system-level consequences. Successful exploitation can allow arbitrary control of freed object contents, redirecting execution or altering security-relevant kernel structures.

Root Cause

The defect is a use-after-free in HTTP.sys request-handling code. The driver retains a pointer to a heap object whose lifecycle is not synchronized with concurrent request processing. When the object is freed while another code path still holds the pointer, subsequent dereference operates on reclaimed memory. An attacker who can influence the contents of the reclaimed allocation can steer kernel execution or manipulate kernel-object state.

Attack Vector

The attack requires network reachability to a service that dispatches requests through HTTP.sys. The attacker must hold a low-privileged authenticated context and must trigger user interaction to complete the exploitation chain. The high attack complexity reflects the timing conditions required to win the race between object free and reuse. Successful exploitation elevates privileges on the target host.

No public proof-of-concept code is available. Consult the Microsoft CVE-2026-69597 Advisory for technical details.

Detection Methods for CVE-2026-69597

Indicators of Compromise

Unexpected System process spawning child processes or loading unusual modules after HTTP request bursts
Kernel bugchecks or HTTP.sys crashes (Event ID 4321 or WER reports referencing HTTP.sys) coincident with anomalous HTTP traffic
Sudden privilege changes for authenticated service accounts interacting with IIS or WinRM endpoints

Detection Strategies

Monitor Windows Error Reporting and kernel crash telemetry for faults inside HTTP.sys correlated to specific source addresses
Baseline HTTP request patterns for IIS and WinRM, then alert on malformed headers, oversized chunked encodings, or race-inducing request floods
Correlate authentication events with post-authentication process creation to identify unexpected token elevation on web-facing hosts

Monitoring Recommendations

Enable HTTP server API logging and IIS request tracing on hosts exposing HTTP.sys to untrusted networks
Forward kernel and Application event logs to a centralized analytics platform for anomaly detection
Track patch state of the Windows HTTP components across the fleet and alert on drift

How to Mitigate CVE-2026-69597

Immediate Actions Required

Apply the Microsoft security update referenced in the Microsoft CVE-2026-69597 Advisory as soon as testing permits
Inventory all hosts exposing services that depend on HTTP.sys, including IIS, WinRM, and third-party applications using the HTTP Server API
Restrict network exposure of HTTP-based management interfaces to trusted administrative networks

Patch Information

Microsoft has published the fix through its Security Update Guide. Deploy the vendor-supplied cumulative update that addresses CVE-2026-69597 on all affected Windows and Windows Server systems. Prioritize internet-exposed and multi-tenant hosts. Validate patch installation by confirming updated file versions of HTTP.sys and rebooting to load the patched driver.

Workarounds

Require strong authentication and network segmentation for services fronted by HTTP.sys until patches are deployed
Disable non-essential HTTP-based services on servers that do not require them, reducing the attack surface of the driver
Enforce least-privilege service accounts so that any successful elevation is bounded by additional access controls

bash

# Verify HTTP.sys driver version on a Windows host after patching
Get-Item C:\Windows\System32\drivers\http.sys | Select-Object Name, VersionInfo

# List installed security updates to confirm the relevant KB is present
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 20