CVE-2026-21240
TOCTOU Race Condition in Windows HTTP.sys Enables Local Privilege Escalation
Publication date: 2026-02-10
Last updated on: 2026-02-11
Assigner: Microsoft Corporation
Description
Description
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| microsoft | windows_10_1809 | to 10.0.17763.8389 (exc) |
| microsoft | windows_server_2019 | to 10.0.17763.8389 (exc) |
| microsoft | windows_server_2022 | to 10.0.20348.4711 (exc) |
| microsoft | windows_server_2025 | to 10.0.26100.32313 (exc) |
| microsoft | windows_11_24h2 | to 10.0.26100.7781 (exc) |
| microsoft | windows_11_24h2 | to 10.0.26100.7781 (exc) |
| microsoft | windows_11_23h2 | to 10.0.22631.6649 (exc) |
| microsoft | windows_11_23h2 | to 10.0.22631.6649 (exc) |
| microsoft | windows_11_25h2 | to 10.0.26200.7781 (exc) |
| microsoft | windows_11_25h2 | to 10.0.26200.7781 (exc) |
| microsoft | windows_server_2022_23h2 | to 10.0.25398.2149 (exc) |
| microsoft | windows_10_22h2 | to 10.0.19045.6937 (exc) |
| microsoft | windows_10_22h2 | to 10.0.19045.6937 (exc) |
| microsoft | windows_10_22h2 | to 10.0.19045.6937 (exc) |
| microsoft | windows_10_21h2 | to 10.0.19044.6937 (exc) |
| microsoft | windows_10_21h2 | to 10.0.19044.6937 (exc) |
| microsoft | windows_10_21h2 | to 10.0.19044.6937 (exc) |
| microsoft | windows_10_1809 | to 10.0.17763.8389 (exc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-367 | The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability is a time-of-check time-of-use (toctou) race condition in Windows HTTP.sys.
It allows an authorized attacker to elevate privileges locally by exploiting this race condition.
How can this vulnerability impact me? :
The vulnerability can lead to elevation of privilege, meaning an attacker with some level of authorization can gain higher privileges on the affected system.
This can result in the attacker gaining greater control over the system, potentially compromising confidentiality, integrity, and availability.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
I don't know
How can this vulnerability be detected on my network or system? Can you suggest some commands?
I don't know
What immediate steps should I take to mitigate this vulnerability?
I don't know