CVE-2026-20809

// CVE-2026-20809 TOCTOU Race Condition PoC (Conceptual) // This is a conceptual demonstration of TOCTOU race condition // Actual exploitation requires precise timing and system-specific conditions #include <windows.h> #include <process.h> #include <stdio.h> // Global flags for synchronization volatile BOOL g_checkCompleted = FALSE; volatile BOOL g_useStarted = FALSE; HANDLE hMutex = NULL; // Thread 1: Performs the check unsigned int __stdcall CheckThread(LPVOID lpParam) { // Simulate TOCTOU vulnerability in kernel memory access // In real scenario: check object ACL/permissions WaitForSingleObject(hMutex, INFINITE); // CHECK PHASE: Verify access permissions printf("[CHECK] Verifying access to kernel object...\n"); BOOL hasAccess = CheckAccessPermissions(); // Simulated check g_checkCompleted = TRUE; ReleaseMutex(hMutex); // Time window between check and use - attacker exploits this Sleep(1); // Minimal delay for race condition return 0; } // Thread 2: Modifies object state during race window unsigned int __stdcall ModifyThread(LPVOID lpParam) { while (!g_checkCompleted) { Sleep(0); // Wait for check to complete } // USE PHASE: Modify object before actual use printf("[MODIFY] Modifying kernel object state during TOCTOU window...\n"); ModifyObjectPermissions(); // Exploit race condition g_useStarted = TRUE; return 0; } // Thread 3: Uses object (vulnerable path) unsigned int __stdcall UseThread(LPVOID lpParam) { while (!g_useStarted) { Sleep(0); } // USE PHASE: Access kernel memory with elevated privileges printf("[USE] Accessing kernel memory with escalated privileges...\n"); AccessKernelMemory(); // Exploit successful return 0; } int main() { printf("CVE-2026-20809 TOCTOU Race Condition PoC\n"); printf("Target: Windows Kernel Memory\n\n"); hMutex = CreateMutex(NULL, FALSE, NULL); HANDLE hThreads[3]; // Create threads to trigger race condition hThreads[0] = (HANDLE)_beginthreadex(NULL, 0, CheckThread, NULL, 0, NULL); hThreads[1] = (HANDLE)_beginthreadex(NULL, 0, ModifyThread, NULL, 0, NULL); hThreads[2] = (HANDLE)_beginthreadex(NULL, 0, UseThread, NULL, 0, NULL); WaitForMultipleObjects(3, hThreads, TRUE, INFINITE); CloseHandle(hThreads[0]); CloseHandle(hThreads[1]); CloseHandle(hThreads[2]); CloseHandle(hMutex); printf("\nRace condition triggered - privilege escalation possible\n"); return 0; } // Simulated functions - actual implementation would require kernel-level access BOOL CheckAccessPermissions() { return FALSE; } void ModifyObjectPermissions() { /* Modify kernel object state */ } void AccessKernelMemory() { /* Gain elevated privileges */ }

{"cve": {"id": "CVE-2026-20809", "sourceIdentifier": "[email protected]", "published": "2026-01-13T18:16:07.360", "lastModified": "2026-01-14T20:11:46.040", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Time-of-check time-of-use (toctou) race condition in Windows Kernel Memory allows an authorized attacker to elevate privileges locally."}, {"lang": "es", "value": "Una condición de carrera de tipo Time-of-check time-of-use (toctou) en la memoria del 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-122"}, {"lang": "en", "value": "CWE-367"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:x64:*", "versionEndExcluding": "10.0.14393.8783", "matchCriteriaId": "9A956D23-259E-450B-8406-FEB2BBED1F39"}, {"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:x86:*", "versionEndExcluding": "10.0.14393.8783", "matchCriteriaId": "41D387B9-5E9D-47CB-B044-D7D10FFFB458"}, {"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:x64:*", "versionEndExcluding": "10.0.17763.8276", "matchCriteriaId": "DD4CBDAB-7626-4048-8474-B1BD9C1F3255"}, {"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:x86:*", "versionEndExcluding": "10.0.17763.8276", "matchCriteriaId": "A6D4C631-2CC0-407C-9ACA-7C151006598C"}, {"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_2012:r2:*:*:*:*:*:*:*", "matchCriteriaId": "DB18C4CE-5917-401E-ACF7-2747084FD36E"}, {"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_server_2016:*:*:*:*:*:*:*:*", "versionEndExcluding": "10.0.14393.8783", "matchCriteriaId": "A059E609-F8D4-4246-BDAE-0AEDED1744D2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_server_2019:*:*:*:*:*:*:*:*", "versionEndExcluding": "10.0.17763.8276", "matchCriteriaId": "A74970A1-CC81-4482-B465-8382B1544EF3"}, {"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-2026-20809", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}