http4s before versions 0.18.26, 0.20.20, and 0.21.2 has a local file inclusion vulnerability. This vulnerability applies to all users of org.http4s.server.staticcontent.FileService, org.http4s.server.staticcontent.ResourceService and org.http4s.server.staticcontent.WebjarService. URI normalization is applied incorrectly. Requests whose path info contain ../ or // can expose resources outside of the configured location. This issue is patched in versions 0.18.26, 0.20.20, and 0.21.2. Note that 0.19.0 is a deprecated release and has never been supported.
The product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize sequences such as ".." that can resolve to a location that is outside of that directory.
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.