borgbackup: crafted archive extraction overwrites files outside target directory

borgbackup is an opensource, deduplicating archiver with compression and authenticated encryption. Prior to 1.4.5 and 2.0.0b22, extracting a malicious archive can follow a symlinked parent path or resolve embedded dot-dot path components and delete or overwrite files outside the extraction directory. A crafted slave hardlink can also use an attacker-controlled hardlink source outside the extraction directory and hard-link that file into the restored tree, disclosing its contents. Creating the malicious archive requires repository access and, for encrypted or authenticated repositories, the Borg key and passphrase; a victim must then extract the archive. This issue is fixed in versions 1.4.5 and 2.0.0b22.