EUVD-2026-44294
GHSA-ccw5-f6hp-583h
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Local use-after-free EoP requiring an existing low-privilege foothold (AV:L, PR:L), low complexity and no user interaction, yielding full SYSTEM-level compromise (C:H/I:H/A:H) without scope change.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
2DescriptionCVE.org
Use after free in Microsoft NAT Helper Components (ipnathlp.dll) allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege escalation in Microsoft's NAT Helper Components (ipnathlp.dll), the driver behind Internet Connection Sharing and NAT translation on Windows 11 (24H2, 25H2, 26H1) and Windows Server 2025. An authenticated attacker who already has low-privilege access can exploit a use-after-free memory corruption bug to run code at higher privilege (SYSTEM). No public exploit identified at time of analysis, and it is not listed in CISA KEV, but Microsoft has released a patch.
Technical ContextAI
ipnathlp.dll implements the Windows NAT Helper / Internet Connection Sharing (ICS) service, which performs network address translation and related session bookkeeping for shared connections. The root cause is CWE-416 (Use After Free): the component frees a memory object but retains and later dereferences a stale pointer, allowing an attacker to control the contents of the reallocated memory and corrupt kernel/service state. Per the CPE data, the affected code ships in Windows 11 Version 24H2, 25H2 and 26H1, plus Windows Server 2025 (including Server Core), meaning the vulnerable DLL is present in the base OS rather than an optional add-on. Use-after-free flaws in privileged local components are a classic and reliable primitive for elevation-of-privilege exploits.
RemediationAI
Patch available per vendor advisory: apply the Microsoft security update for CVE-2026-58537 documented at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-58537, selecting the KB that matches each affected SKU (Windows 11 24H2/25H2/26H1 and Windows Server 2025 including Server Core). No exact fixed version string was included in the input, so pull the precise build from the MSRC guide before validating. As a compensating control where immediate patching is not possible, disable Internet Connection Sharing / the NAT Helper (SharedAccess) service on hosts that do not need to share a network connection, since ipnathlp.dll backs that functionality - the trade-off is loss of ICS/NAT sharing on those machines. Because exploitation requires local low-privileged access, also tighten who can run code on affected systems and monitor for unexpected privilege escalation, but these are supplements to, not replacements for, the vendor patch.
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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