Instead of trying to find "bad" characters like .. , only allow "good" characters (alphanumeric). If the input doesn't match the pattern, reject it immediately.
| Component | Meaning | |-----------|---------| | -template- | Likely a prefix added by the attacker to bypass a “starts with” filter. For example, a WAF rule might allow any parameter that begins with "template" . By prepending -template- , the attacker satisfies that condition while still embedding the traversal sequence. | | ..-2F | This is an obfuscated ../ . The standard ..%2F becomes ..-2F after replacing % with - . Each occurrence represents one level up in the directory hierarchy. | | (Repeated four times) | The attacker uses four consecutive ..-2F sequences to climb up four directory levels. | | root-2F | This is an obfuscated root/ (again -2F stands for / ). The attacker is likely trying to reach the /root/ directory—the home folder of the root user on Linux systems, which often contains highly sensitive data like SSH keys, bash history, or automation scripts. |
: Ensure the web server user (e.g., www-data or nginx ) has restricted permissions. It should never have access to the /root/ directory or sensitive system files.
: Expose application source code, allowing attackers to find further vulnerabilities. -template-..-2F..-2F..-2F..-2Froot-2F
Path traversal, also known as directory traversal, is a web security vulnerability that allows an attacker to read arbitrary files on the server that runs an application. This can include application source code, configuration files containing credentials, and critical operating system files.
An application has a download feature:
The server constructs the path: /var/cms/templates/-template-..-2F..-2F..-2F..-2Froot-2F.bashrc Instead of trying to find "bad" characters like
If a web server is designed to load files from a specific folder (like www/images/ ), a normal request looks like this:
A typical attack might look like:
In the context of the string -template-..-2F..-2F..-2F..-2Froot-2F : | Component | Meaning | |-----------|---------| | -template-
: Instead of letting users request a file by name/path, use an ID or a token that maps to a specific file on the backend.
, you’re looking at an active attempt to compromise a server’s file system. What is Path Traversal?
To safely handle paths in a Node.js environment, you might use the path module:
By combining path traversal with Local File Inclusion (LFI), an attacker can point the application to a file containing malicious code (like log files poisoned with PHP code or uploaded session files), forcing the server to execute it.
Below is a comprehensive technical article analyzing this specific vulnerability pattern, how it works, and how to defend against it.