Bzip2 is a data compressor.
A bug was found in the way bzgrep processes file names. If a user can be tricked into running bzgrep on a file with a carefully crafted file name, arbitrary commands could be executed as the user running bzgrep. The Common Vulnerabilities and Exposures project (cve.mitre.org) has assigned the name CVE-2005-0758 to this issue.
A bug was found in the way bzip2 modifies file permissions during decompression. If an attacker has write access to the directory into which bzip2 is decompressing files, it is possible for them to modify permissions on files owned by the user running bzip2 (CVE-2005-0953).
A bug was found in the way bzip2 decompresses files. It is possible for an attacker to create a specially crafted bzip2 file which will cause bzip2 to cause a denial of service (by filling disk space) if decompressed by a victim (CVE-2005-1260).
Users of Bzip2 should upgrade to these updated packages, which contain backported patches to correct these issues.