Erik Sjölund discovered that hztty, a converter for GB, Big5 and zW/HZ Chinese encodings in a tty session, can be triggered to execute arbitrary commands with group utmp privileges.
For the stable distribution (woody) this problem has been fixed in version 2.0-5.2woody2.
For the unstable distribution (sid) this problem has been fixed in version 2.0-6.1.
We recommend that you upgrade your hztty package.
MD5 checksums of the listed files are available in the original advisory.