melange QEMU runner could write files outside workspace directory

An attacker who can influence the tar stream from a QEMU guest VM could write files outside the intended workspace directory on the host. The retrieveWorkspace function extracts tar entries without validating that paths stay within the workspace, allowing Path Traversal via ../ sequences.

Fix: Fixed in 6e243d0d. Merged in release.

Acknowledgements

melange thanks Oleh Konko from 1seal for discovering and reporting this issue.