-page-....-2f-2f....-2f-2f....-2f-2fetc-2fpasswd May 2026

The observed payload is:
-page-....-2F-2F....-2F-2F....-2F-2Fetc-2Fpasswd

The -page- suggests a parameter name or delimiter, while each .. escapes one directory level. The final target is /etc/passwd (a Unix file listing user accounts).

The purpose of this report is to analyze the provided string as a cybersecurity indicator, explain:

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CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

Attackers use sequences like ../ to move up directories and access files outside the web root.

Example vulnerable code (PHP):

$page = $_GET['page'];
include("/var/www/pages/" . $page . ".php");

If page=../../../etc/passwd%00 (null byte injection in older PHP), the server might read /etc/passwd.

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Introduction

In Unix and Linux operating systems, the /etc/passwd file plays a critical role in user management. It is a text file that contains a list of all registered users on the system. Understanding the structure and content of this file is essential for system administrators to manage user accounts effectively and ensure system security.

The Structure of /etc/passwd

Each line in the /etc/passwd file represents a user, and it is divided into several fields separated by colons (:). A typical entry in the /etc/passwd file looks like this: -page-....-2F-2F....-2F-2F....-2F-2Fetc-2Fpasswd

username:x:UID:GID:GECOS:home_directory:login_shell

Example:

john:x:1001:1001:John Doe:/home/john:/bin/bash

Security Considerations

The /etc/passwd file is readable by all users on the system, which allows for the retrieval of usernames and associated information. However, to enhance security, passwords are no longer stored in /etc/passwd. Instead, they are kept in /etc/shadow, which is only readable by root, ensuring that only authorized users can access the passwords.

Managing Users

System administrators can edit the /etc/passwd file directly to make changes to user accounts, but this is generally discouraged. Instead, commands like useradd, usermod, and userdel are used to manage users safely and ensure data consistency. The observed payload is: -page-

Conclusion

The /etc/passwd file is a vital component of Unix and Linux systems, providing essential user information. Its format and use are foundational to understanding system administration and security. Proper management and understanding of this file are critical for maintaining a secure and efficiently run system.

Path traversal (directory traversal) attacks allow attackers to access arbitrary files by manipulating input that is concatenated with a base directory. This paper examines a specific encoded payload, decodes it, explains how it works against vulnerable web parameters, and discusses detection and prevention.

The attacker used -2F instead of %2F (standard URL encoding) or / directly. This could be:

Similar bypasses include:

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