The problem can be corrected by upgrading the affected package to
version 5.8.4-2ubuntu0.5 (for Ubuntu 4.10), 5.8.4-6ubuntu1.1 (for
Ubuntu 5.04), or 5.8.7-5ubuntu1.1 (for Ubuntu 5.10). In general, a
standard system upgrade is sufficient to effect the necessary changes.
Jack Louis of Dyad Security discovered that Perl did not sufficiently
check the explicit length argument in format strings. Specially
crafted format strings with overly large length arguments led to a
crash of the Perl interpreter or even to execution of arbitrary
attacker-defined code with the privileges of the user running the Perl
However, this attack was only possible in insecure Perl programs which
use variables with user-defined values in string interpolations
without checking their validity.