Vulnerabilities
CVE-2026-108399: Local Privilege Escalation via Heap Overflow in Windows Hyper‑V
A heap‑based buffer overflow in Windows Hyper‑V permits a local attacker with authorized access to gain elevated privileges. The vulnerability exists in all current Hyper‑V releases and can be mitigated by applying the latest Microsoft security update or disabling Hyper‑V when not required.
What Happened
A heap‑based buffer overflow in the Hyper‑V hypervisor was discovered. The flaw allows an attacker with local, authorized privileges to execute arbitrary code in the context of the Hyper‑V service, effectively elevating their privileges to system level.
Severity: Critical – Local privilege escalation with potential for full system compromise.
Impact
Any user with local access to a machine running Hyper‑V can exploit the flaw. Successful exploitation results in full system compromise, enabling the attacker to tamper with virtual machines, steal data, or pivot to other hosts.
Mitigation
- Apply the Microsoft Security Update released for CVE‑2026‑108399 (KB…).
- If Hyper‑V is not required, disable the feature via Server Manager or PowerShell: Disable-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V.
- Restrict local user permissions to the minimum necessary; avoid granting administrative rights to users who only need to manage VMs.
Recommendations
Verify that the latest cumulative update for Windows Server 2022/2025/2026 is installed. Monitor the Windows Security Center for any additional advisories. Conduct a rapid assessment of all Hyper‑V hosts to confirm patch status and enforce least‑privilege policies.
Related vulnerabilities
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A heap-based buffer overflow in Windows Desktop Window Manager allows a local attacker to gain elevated privileges. The flaw affects all Windows systems running DWM and can be mitigated by applying the latest security update. Defenders should verify patch status and monitor for privilege escalation events.
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CVE-2026-70114: Windows Kernel Heap Overflow Enables Local Privilege Escalation
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A heap‑based buffer overflow in the Windows TCP/IP stack (CVE‑2026‑83678) allows a local attacker with authorized access to elevate privileges. Microsoft has issued a patch; administrators should apply it immediately and tighten local privilege controls.
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