`melange update-cache` has unbounded HTTP download that can exhaust disk in CI

melange update-cache downloads URIs from build configs via io.Copy without any size limit or HTTP client timeout (pkg/renovate/cache/cache.go). An attacker-controlled URI in a melange config can cause unbounded disk writes, exhausting disk on the build runner. Affected versions <= 0.40.5.

Fix: Merged
Acknowledgements

Thank you to Oleh Konko from 1seal for discovering and reporting this issue.