Velero vulnerable to file path traversal when extracting from backup's tarball

Impact

What kind of vulnerability is it? Who is impacted? If the attacker compromises the backup's object storage backend and uploads a malicious backup tarball including file names like the following:

• ../../../tmp/escape_1 -> file created at /tmp/escape_1
• ../../../../../../../../tmp/escape_2 -> file created at /tmp/escape_2
• ../../../tmp/cron_poc -> would be /etc/cron.d/backdoor in real attack
• ../../../tmp/ssh_poc -> would be ~/.ssh/authorized_keys
• ../../../tmp/kubeconfig_poc -> would be ~/.kube/config

It's possible that extracting files from the tarball during restore can overwrite sensitive files in the Velero pod filesystem.

Patches

Has the problem been patched? What versions should users upgrade to?

By far, there is no patch yet. We are working on the main branch, then cherry-pick to the release-1.18 for v1.18.1 patch.

Workarounds

Is there a way for users to fix or remediate the vulnerability without upgrading?

There is no workaround, but the good news is that keeping your OSS safe will prevent the vulnerability.