CWE-30: Path Traversal: '\dir\..\filename'
The product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize '\dir\..\filename' (leading backslash dot dot) sequences that can resolve to a location that is outside of that directory.
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Overview
This allows attackers to traverse the file system to access files or directories that are outside of the restricted directory. This is similar to CWE-26, except using "\" instead of "/". The '\dir\..\filename' manipulation is useful for bypassing some path traversal protection schemes. Sometimes a program only checks for "..\" at the beginning of the input, so a "\..\" can bypass that check.
Common consequences
What can happen when CWE-30 is exploited.
Read Files or Directories, Modify Files or Directories
Affects: Confidentiality, Integrity
How it happens
When it is introduced
Typically introduced during these phases of the software lifecycle.
Applies to
Operating systems
How to prevent it
Practical mitigations for CWE-30, grouped by where in the lifecycle they apply.