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
While a specific "official" write-up might be hosted on private CTF platforms (like Hack The Box or specific university labs), the challenge typically revolves around exploiting a implementation that handles .1zip files. Challenge Overview
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) lhfs_1zip
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 . Upload or pass this file to the lhfs binary
The first step in these challenges is usually reverse-engineering the .1zip header. Typically, the format includes: A sequence (e.g., 1ZIP ). Metadata for file count and individual file lengths. Filenames followed by the raw File Content . 2. Identifying the Vulnerability
A service or binary that parses a custom archive format called .1zip . Challenge Overview Creating a symlink inside the archive
If the extraction tool doesn't sanitize filenames, you can use ../ to write files outside the intended directory (e.g., overwriting .ssh/authorized_keys or /etc/passwd ).