BuildKit is a toolkit for converting source code to build artifacts in an efficient, expressive and repeatable manner. A malicious BuildKit frontend or Dockerfile using RUN --mount could trick the feature that removes empty files created for the mountpoints into removing a file outside the container, from the host system. The issue has been fixed in v0.12.5. Workarounds include avoiding using BuildKit frontends from an untrusted source or building an untrusted Dockerfile containing RUN --mount feature. A vulnerability was found in the Moby Builder Toolkit, which arose from BuildKit's attempts to clean up temporarily added directories after use. A malicious BuildKit frontend or Dockerfile using RUN --mount could deceive the feature responsible for removing empty files created for the mount points, potentially leading to removing a file outside the container and affecting the host system. Successful exploitation of this issue may result in the arbitrary deletion of files and directories on the underlying host OS when building an image using a malicious Dockerfile or upstream image (for example, when using FROM).
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