CVE-2026-55828: go.qbee.io/transport: Symlink-chain path traversal in tar extraction (one level outside destination)

The go.qbee.io/transport library is affected by a symlink-chain path traversal vulnerability in its extractTar routine. The library’s path validation is strictly lexical and fails to account for on-disk symlinks created earlier in the extraction process. Consequently, a crafted tar archive can be used to write or overwrite files one directory level above the intended extraction path. In the case of qbee-agent, which runs with root privileges, this vulnerability permits a root-privileged file write outside the intended destination.