diffoscope before 256 allows directory traversal via an embedded filename in a GPG file. Contents of any file, such as ../.ssh/id_rsa, may be disclosed to an attacker. This occurs because the value of the gpg --use-embedded-filenames option is trusted.
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.