CAPEC-139

Description

An attacker exploits a weakness in input validation on the target by supplying a specially constructed path utilizing dot and slash characters for the purpose of obtaining access to arbitrary files or resources. An attacker modifies a known path on the target in order to reach material that is not available through intended channels. These attacks normally involve adding additional path separators (/ or \) and/or dots (.), or encodings thereof, in various combinations in order to reach parent directories or entirely separate trees of the target's directory structure.

Prerequisites

The target application must accept a string as user input, fail to sanitize combinations of characters in the input that have a special meaning in the context of path navigation, and insert the user-supplied string into path navigation commands.

Mitigations

Design: Input validation. Assume that user inputs are malicious. Utilize strict type, character, and encoding enforcement

Implementation: Perform input validation for all remote content, including remote and user-generated content.

Implementation: Validate user input by only accepting known good. Ensure all content that is delivered to client is sanitized against an acceptable content specification -- using an allowlist approach.

Implementation: Prefer working without user input when using file system calls

Implementation: Use indirect references rather than actual file names.

Implementation: Use possible permissions on file access when developing and deploying web applications.

Skills Required

[Low] To inject the malicious payload in a web page

[High] To bypass non trivial filters in the application