Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Local EoP requiring an existing low-privileged foothold (AV:L, PR:L), no user interaction, with kernel-context compromise yielding full C/I/A impact.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
2DescriptionCVE.org
Use after free in Windows TCP/IP allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege elevation in the Microsoft Windows TCP/IP networking stack lets an already-authenticated, low-privileged user corrupt kernel memory via a use-after-free (CWE-416) and gain SYSTEM-level control. The flaw affects a broad range of client and server SKUs from Windows 10 1607 through Windows 11 26H1 and Windows Server 2012 through Server 2025, including Server Core installations. Microsoft reported the issue and has released a patch; there is no public exploit identified at time of analysis and the CVE is not listed in CISA KEV.
Technical ContextAI
The vulnerability resides in Windows TCP/IP, implemented primarily in the tcpip.sys kernel driver that handles IPv4/IPv6, TCP, UDP and related packet processing in kernel mode. CWE-416 (Use After Free) indicates code continues to reference a kernel object after its backing memory has been freed; an attacker who can influence allocation and free timing can reclaim that memory with controlled data and steer execution or corrupt kernel structures. Because tcpip.sys runs in the kernel, successful exploitation yields kernel-context privileges. The affected CPE set spans Windows 10 (1607, 1809, 21H2, 22H2), Windows 11 (24H2, 25H2, 26H1) and Windows Server 2012/2012 R2/2016/2019/2022/2025, indicating a shared component present across the entire supported Windows line.
RemediationAI
Apply the vendor-released Microsoft security update for CVE-2026-50306 for your specific Windows build; the patch is available per the MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50306, which lists the exact fixed KB/build for each SKU (deploy the version matching your OS). Prioritize multi-user, RDP/terminal, and shared jump hosts where untrusted users hold local accounts, since those most directly expose the local attack surface. No specific vendor workaround is documented; as a compensating control until patching, restrict interactive and standard-user login rights on sensitive hosts and enforce least privilege and application allow-listing to raise the bar for an attacker gaining the initial low-privileged foothold this bug requires - note these controls reduce but do not eliminate exposure, since any authenticated local user could still trigger the flaw.
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Same weakness CWE-416 – Use After Free
View allSame technique Use After Free
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External POC / Exploit Code
Leaving vuln.today
EUVD-2026-43857
GHSA-pr8p-w98x-r7fw