The product contains protection mechanisms to restrict access to 'realdir/filename', but it constructs pathnames using external input in the form of 'fakedir/../realdir/filename' that are not handled by those mechanisms. This allows attackers to perform unauthorized actions against the targeted file.
Proxy allows remote attackers to bypass denylist restrictions and connect to unauthorized web servers by modifying the requested URL, including (1) a // (double slash), (2) a /SUBDIR/.. where the desired file is in the parentdir, (3) a /./, or (4) URL-encoded characters.
Impact: Read Files or Directories, Modify Files or Directories — Notes:
Potential Mitigations
Implementation: Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked. (N/A)
Applicable Platforms
None (Not Language-Specific, Undetermined)
Demonstrative Examples
N/A
Notes
Theoretical: This is a manipulation that uses an injection for one consequence (containment violation using relative path) to achieve a different consequence (equivalence by alternate name).