Controlled Path Traversal Allowing Symbolic Link Creation in Debusine Package Parser

Debusine is an integrated solution to build, distribute and maintain a Debian-based distribution. Debian source packages (.dsc) and upload artifacts (.changes) are manifest files that name the files that make up the artifact. The parser used to read these files in Debusine accepted arbitrary fully user-controlled paths. The mergeuploads task could be abused to create arbitrary symbolic links on a worker, overwriting any file that the worker user has access to.

Debusine is an integrated solution to build, distribute and maintain a Debian-based distribution. Files managed by debusine are organized into artifacts. The endpoints that create and delete relationships between artifacts enforced no permissions checks beyond being able to see the artifacts in question.