Issue name

File path traversal

Typical severity

High

Issue description

File path traversal vulnerabilities arise when user-controllable data is used within a filesystem operation in an unsafe manner. Typically, a user-supplied filename is appended to a directory prefix in order to read or write the contents of a file. If vulnerable, an attacker can supply path traversal sequences (using dot-dot-slash characters) to break out of the intended directory and read or write files elsewhere on the filesystem.

This is typically a very serious vulnerability, enabling an attacker to access sensitive files containing configuration data, passwords, database records, log data, source code, and program scripts and binaries.

Issue remediation

Ideally, application functionality should be designed in such a way that user-controllable data does not need to be passed to filesystem operations. This can normally be achieved by referencing known files via an index number rather than their name, and using application-generated filenames to save user-supplied file content.

If it is considered unavoidable to pass user-controllable data to a filesystem operation, three layers of defense can be employed to prevent path traversal attacks:

References

Vulnerability classifications