EUVD-2026-44255
GHSA-x5vq-pv82-hp56
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Local vector requiring an existing low-privilege session (AV:L/PR:L), low complexity with no interaction, and full SYSTEM compromise gives high C/I/A within unchanged scope.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
2DescriptionCVE.org
Use after free in Windows Kernel allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege escalation in the Microsoft Windows Kernel (CWE-416 use-after-free) lets an already-authenticated low-privilege user corrupt kernel memory and gain SYSTEM-level control across a broad range of Windows 10, Windows 11, and Windows Server 2016 through 2025 builds. Microsoft self-reported the flaw and has shipped a patch through the Update Guide; there is no public exploit identified at time of analysis and it is not listed in CISA KEV. With CVSS 7.8 (AV:L/PR:L) it is a classic Patch-Tuesday local EoP suitable as a second-stage primitive after initial access.
Technical ContextAI
The Windows Kernel (ntoskrnl and associated kernel-mode components) is the trusted core that mediates all process, memory, and hardware access. This is a CWE-416 use-after-free: a kernel object is freed while a reference to it is still reachable, so subsequent operations dereference a dangling pointer. An attacker who can influence reallocation of the freed slab can groom kernel pool memory to place attacker-controlled data at the stale location, converting the dangling reference into a controlled read/write or execution primitive in ring 0. The CPE set indicates the vulnerable code path is present across Windows 10 (1607, 1809, 21H2, 22H2), Windows 11 (24H2, 25H2, 26H1), and Windows Server 2016/2019/2022/2025 including Server Core, implying the defect lives in a long-lived, widely shared kernel component rather than a version-specific feature.
RemediationAI
Apply the Microsoft security update for CVE-2026-56643 for your specific Windows build - Patch available per vendor advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56643, where the exact KB and patched build for each affected SKU (Windows 10 1607-22H2, Windows 11 24H2-26H1, Server 2016-2025 including Server Core) are listed; no standalone fix version string was provided in the input, so pull the correct KB from that advisory. Because the vulnerability is a kernel-level use-after-free with no vendor-documented configuration workaround, the update is the only reliable fix. As compensating controls until patching, reduce the pool of accounts that can obtain the required local low-privilege foothold: enforce least privilege and remove unnecessary local/interactive logon rights, restrict who can run untrusted code on servers (trade-off: tighter app allowlisting/AppLocker or WDAC can break legitimate line-of-business tooling), and monitor EDR for kernel-exploitation and token-manipulation behaviors (trade-off: detective, not preventive). Prioritize multi-user and RDP-exposed hosts where low-privilege users are most likely present.
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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