Gaël Delalleau discovered a buffer overflow in the handling of the LINEMODE suboptions in telnet clients. Heimdal, a free implementation of Kerberos 5, also contains such a client. This can lead to the execution of arbitrary code when connected to a malicious server.
For the old stable distribution (woody) this problem has been fixed in version 0.4e-7.woody.11.
For the stable distribution (sarge) this problem has been fixed in version 0.6.3-10.
For the unstable distribution (sid) this problem has been fixed in version 0.6.3-10.
We recommend that you upgrade your heimdal package.
MD5 checksums of the listed files are available in the original advisory.