unarj: Long filenames buffer overflow and a path traversal vulnerability

Background

unarj is an ARJ archive decompressor.

Description

unarj has a bounds checking vulnerability within the handling of long filenames in archives. It also fails to properly sanitize paths when extracting an archive (if the “x” option is used to preserve paths).

Impact

An attacker could trigger a buffer overflow or a path traversal by enticing a user to open an archive containing specially-crafted path names, potentially resulting in the overwrite of files or execution of arbitrary code with the permissions of the user running unarj.

Workaround

There is no known workaround at this time.

Resolution

All unarj users should upgrade to the latest version:

 # emerge --sync
 # emerge --ask --oneshot --verbose ">=app-arch/unarj-2.63a-r2"