CAPEC-139: Relative Path Traversal
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.
- Likelihood of attack
- High
- Typical severity
- High
- Abstraction
- DetailedA low-level, detailed pattern, often for a particular technology.
Mechanism of attack: Manipulate Data Structures
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.
Skills required
- LowTo inject the malicious payload in a web page
- HighTo bypass non trivial filters in the application
Consequences
- Integrity
Modify Data
- Confidentiality
Read Data
- ConfidentialityIntegrityAvailability
Execute Unauthorized Commands
Run Arbitrary Code
- Access Control
Bypass Protection Mechanism
- Availability
Unreliable Execution
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.