The software 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.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.