CVE-2026-54727: proot-distro has a Container Isolation Bypass via Crafted Restore Archive

When restoring a crafted backup archive, proot-distro restore accepts hardlink entries whose source path references a different installed container.

The restore logic resolves the hardlink source from the archive’s linkname field and copies the referenced file into the container identified by the archive entry.

Although path traversal protections correctly keep the source path inside the proot-distro containers directory, no validation ensures that the hardlink source container matches the destination container.

As a result, a malicious backup archive can copy files between otherwise isolated containers, enabling both cross-container disclosure and cross-container file injection.