CAPEC Details
Name Manipulating Writeable Terminal Devices
Likelyhood of attack Typical severity
High Very High
Summary This attack exploits terminal devices that allow themselves to be written to by other users. The attacker sends command strings to the target terminal device hoping that the target user will hit enter and thereby execute the malicious command with their privileges. The attacker can send the results (such as copying /etc/passwd) to a known directory and collect once the attack has succeeded.
Prerequisites User terminals must have a permissive access control such as world writeable that allows normal users to control data on other user's terminals.
Execution Flow
Step Phase Description Techniques
1 Explore [Identify attacker-writable terminals] Determine if users TTYs are writable by the attacker.
  • Determine the permissions for the TTYs found on the system. Any that allow user write to the TTY may be vulnerable.
  • Attempt to write to other user TTYs. This approach could leave a trail or alert a user.
2 Exploit [Execute malicious commands] Using one or more vulnerable TTY, execute commands to achieve various impacts.
  • Commands that allow reading or writing end user files can be executed.
Solutions Design: Ensure that terminals are only writeable by named owner user and/or administrator Design: Enforce principle of least privilege
Related Weaknesses
CWE ID Description
CWE-77 Improper Neutralization of Special Elements used in a Command ('Command Injection')
Related CAPECS
CAPEC ID Description
CAPEC-248 An adversary looking to execute a command of their choosing, injects new items into an existing command thus modifying interpretation away from what was intended. Commands in this context are often standalone strings that are interpreted by a downstream component and cause specific responses. This type of attack is possible when untrusted values are used to build these command strings. Weaknesses in input validation or command construction can enable the attack and lead to successful exploitation.