The Tar program provides the ability to create and manipulate tar archives.
Tar attempts to avoid path traversal attacks by removing offending parts of the element name at extract. This sanitizing leads to a vulnerability where the attacker can bypass the path name(s) specified on the command line.
The attacker can create a crafted tar archive that, if extracted by the victim, replaces files and directories the victim has access to in the target directory, regardless of the path name(s) specified on the command line.
There is no known workaround at this time.
All Tar users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=app-arch/tar-1.29-r1"