CVE-2026-27921
Race Condition in Windows TCP/IP Enables Local Privilege Escalation
Publication date: 2026-04-14
Last updated on: 2026-04-22
Assigner: Microsoft Corporation
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| microsoft | windows_server_2012 | r2 |
| microsoft | windows_server_2012 | * |
| microsoft | windows_10_1607 | to 10.0.14393.9060 (exc) |
| microsoft | windows_10_1607 | to 10.0.14393.9060 (exc) |
| microsoft | windows_10_1809 | to 10.0.17763.8644 (exc) |
| microsoft | windows_10_1809 | to 10.0.17763.8644 (exc) |
| microsoft | windows_10_21h2 | to 10.0.19044.7184 (exc) |
| microsoft | windows_10_21h2 | to 10.0.19044.7184 (exc) |
| microsoft | windows_10_21h2 | to 10.0.19044.7184 (exc) |
| microsoft | windows_10_22h2 | to 10.0.19045.7184 (exc) |
| microsoft | windows_10_22h2 | to 10.0.19045.7184 (exc) |
| microsoft | windows_10_22h2 | to 10.0.19045.7184 (exc) |
| microsoft | windows_11_23h2 | to 10.0.22631.6936 (exc) |
| microsoft | windows_11_23h2 | to 10.0.22631.6936 (exc) |
| microsoft | windows_11_24h2 | to 10.0.26100.8246 (exc) |
| microsoft | windows_11_24h2 | to 10.0.26100.8246 (exc) |
| microsoft | windows_11_25h2 | to 10.0.26200.8246 (exc) |
| microsoft | windows_11_25h2 | to 10.0.26200.8246 (exc) |
| microsoft | windows_11_26h1 | to 10.0.28000.1836 (exc) |
| microsoft | windows_11_26h1 | to 10.0.28000.1836 (exc) |
| microsoft | windows_server_2016 | to 10.0.14393.9060 (exc) |
| microsoft | windows_server_2019 | to 10.0.17763.8644 (exc) |
| microsoft | windows_server_2022 | to 10.0.20348.5020 (exc) |
| microsoft | windows_server_2022_23h2 | to 10.0.25398.2274 (exc) |
| microsoft | windows_server_2025 | to 10.0.26100.32690 (exc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-416 | The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer. |
| CWE-362 | The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently. |
Attack-Flow Graph
AI Powered Q&A
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
This vulnerability allows an authorized attacker to elevate privileges locally by exploiting a race condition in Windows TCP/IP.
Elevation of privilege vulnerabilities can potentially lead to unauthorized access to sensitive data or systems, which may impact compliance with standards and regulations such as GDPR and HIPAA that require protection of personal and health information.
However, no specific information is provided about direct effects on compliance with these regulations.
Can you explain this vulnerability to me?
This vulnerability is a race condition in the Windows TCP/IP stack caused by concurrent execution using a shared resource without proper synchronization. It allows an authorized local attacker to exploit this flaw to elevate their privileges on the affected system.
How can this vulnerability impact me? :
An attacker who already has some level of access to the system can exploit this vulnerability to gain higher privileges. This elevation of privilege can allow the attacker to perform actions that are normally restricted, potentially compromising system integrity, confidentiality, and availability.
What immediate steps should I take to mitigate this vulnerability?
This vulnerability allows an authorized attacker to elevate privileges locally due to a race condition in Windows TCP/IP.
To mitigate this vulnerability, it is recommended to apply the security updates provided by Microsoft as detailed in their official update guide.
Ensure that your Windows systems are fully patched with the latest security updates from Microsoft.