Title: Windows 11 25H2 Hyper-V CVE-2026-21248 Heap Overflow + Ghost Patch Exploit Framework Author: nu11secur1ty Date: 2026-02-13 CVE: CVE-2026-21248, CVE-2026-21244 Type: Local / Remote (misclassified) Platform: Windows 11 25H2 Build 26200.7830 (x64) Download: https://github.com/nu11secur1ty/CVE-mitre/tree/main/2026/CVE-2026-21248 Description: ----------- This is a complete weaponization framework for CVE-2026-21248, a heap-based buffer overflow in Windows Hyper-V VMBus GPADL allocation. The framework PROVES that Microsoft misrepresented this CVE (PR:N vs actual PR:L), demonstrates that the entire patch trust model is forgeable via registry manipulation, and achieves Ring -1 persistence by replacing hvax64.exe with an unsigned hypervisor. Key findings demonstrated: ------------------------- ✅ CVSS Misclassification: Microsoft claims PR:N (No privileges) but PROVEN to require Hyper-V Administrator (PR:L) ✅ Patch Trust Model Broken: Microsoft relies on HKLM\...\PatchLevel registry key — trivially forgeable ✅ Scanners are Blind: Nessus/Tenable/Qualys only check registry, never test the overflow ✅ Ring -1 Persistence: hvax64.exe loads unsigned hypervisor code — achieved ✅ Telemetry Subversion: Local admin can kill all Microsoft telemetry ✅ Permanent victory signature written to C:\Windows\win.ini The framework operates in two modes: ---------------------------------- 1. NORMAL USER: Generates malicious .vhdx trigger and tests privilege requirements 2. ADMINISTRATOR: Installs Ring -1 backdoor, forges patch registry, kills telemetry, writes win.ini signature --- PROOF OF CONCEPT LOG --- PROOF A: Privilege Requirement Test (Normal User, No Hyper-V Admin) -------------------------------------------------------------------- PS C:\Users\MicroProblems> python .\cve-2026-21248.py [*] Phase 2: Triggering CVE-2026-21248 heap overflow... [!] Mount failed: You do not have the required permission [!] User lacks Hyper-V Administrator privileges [!] This proves CVE-2026-21248 requires PR:L not PR:N PROOF B: Overflow Triggers WITH Hyper-V Admin Rights ---------------------------------------------------- After adding user to 'Hyper-V Administrators' group: [*] Phase 2: Triggering CVE-2026-21248 heap overflow... [+] VHDX mounted successfully - overflow triggered PROOF C: Ghost Patch Registry Forge ----------------------------------- [*] Phase 4: Installing ghost patch registry... [+] HKLM\...\HyperV\Security\PatchLevel = 202602 Windows Update now reports: "Fully patched" Nessus now reports: "Not Vulnerable" REALITY: Ring -1 backdoor active PROOF D: win.ini Victory Signature ----------------------------------- C:\Windows\win.ini contains: ; CVE-2026-21248 PATCH FAILURE — nu11secur1ty was here ; Hyper-V Ghost Patch State — Weaponized ; Microsoft KB5077181 Registry Key: FORGED ; Hypervisor: nu11secur1ty backdoor (Ring -1) PROOF E: Tenable/Nessus Confirms Blindness ------------------------------------------ Plugin 298551 documentation: "Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number." --- ADDITIONAL NOTES --- Versions affected: Windows 11 25H2 Build 26200.7830 (pre-patch) Patched version: Build 26200.7840 (KB5077181) This framework demonstrates that Microsoft's CVSS scoring for CVE-2026-21248 is incorrect, their patch trust model is completely forgeable, and every major scanner is blind to this attack vector. The researcher has achieved Ring -1 persistence and left permanent proof in win.ini. Full source code and documentation available at: https://github.com/nu11secur1ty/CVE-mitre/tree/main/2026/CVE-2026-21248 — nu11secur1ty, 2026