The Permission Model assumes that any path starting with two backslashes \ has a four-character prefix that can be ignored, which is not always true. This subtle bug leads to vulnerable edge cases.
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.