If you are writing the "defense" side of this write-up, the fix is to the extraction process or strictly sanitize filenames to remove any .. or leading / characters. g., PicoCTF, SECCON, or HTB) where this challenge appeared?
If the goal is to read a flag located at /flag.txt , the exploit usually involves crafting a malicious .1zip file: Manually create a file with the 1ZIP header. Payload: Set the filename field to ../../../../flag.txt . lhfs_1zip
Most variations of this challenge focus on Path Traversal or Buffer Overflows within the extraction logic. Technical Breakdown & Solution Steps 1. File Format Analysis If you are writing the "defense" side of
Creating a symlink inside the archive that points to a sensitive system file. When the service "updates" or "reads" the file, it interacts with the system target instead. 3. Exploitation (General Example) If the goal is to read a flag located at /flag
Upload or pass this file to the lhfs binary. If vulnerable, it will attempt to "extract" the file to that path or read from it, often leaking the contents in the process. Common Mitigation
A service or binary that parses a custom archive format called .1zip .