CAPEC-27: Leveraging Race Conditions via Symbolic Links

Description
This attack leverages the use of symbolic links (Symlinks) in order to write to sensitive files. An attacker can create a Symlink link to a target file not otherwise accessible to them. When the privileged program tries to create a temporary file with the same name as the Symlink link, it will actually write to the target file pointed to by the attackers' Symlink link. If the attacker can insert malicious content in the temporary file they will be writing to the sensitive file by using the Symlink. The race occurs because the system checks if the temporary file exists, then creates the file. The attacker would typically create the Symlink during the interval between the check and the creation of the temporary file.
Extended Description

Many client applications use specific query templates when interacting with a server and often automatically fill in specific fields or attributes. If the server does not verify that the query matches one of the expected templates, an adversary who is allowed to send normal queries could modify their query to try to return additional information. The adversary may not know the names of fields to request or how other modifications will affect the server response, but by attempting multiple plausible variants, they might eventually trigger a server response that divulges sensitive information. Other possible outcomes include server crashes and resource consumption if the unexpected queries cause the server to enter an unstable state or perform excessive computation.

Severity :

High

Possibility :

Medium

Type :

Detailed
Relationships with other CAPECs

This table shows the other attack patterns and high level categories that are related to this attack pattern.

CAPEC-29: Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions
Prerequisites

This table shows the other attack patterns and high level categories that are related to this attack pattern.

  • The attacker is able to create Symlink links on the target host.
  • Tainted data from the attacker is used and copied to temporary files.
  • The target host does insecure temporary file creation.
Skills required

This table shows the other attack patterns and high level categories that are related to this attack pattern.

  • Medium This attack is sophisticated because the attacker has to overcome a few challenges such as creating symlinks on the target host during a precise timing, inserting malicious data in the temporary file and have knowledge about the temporary files created (file name and function which creates them).
Taxonomy mappings

Mappings to ATT&CK, OWASP and other frameworks.

Related CWE

A Related Weakness relationship associates a weakness with this attack pattern. Each association implies a weakness that must exist for a given attack to be successful.

CWE-61: UNIX Symbolic Link (Symlink) Following

CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition

CWE-662: Improper Synchronization

CWE-667: Improper Locking

CWE-689: Permission Race Condition During Resource Copy

Visit http://capec.mitre.org/ for more details.