Multiple integer underflows in the (1) AES and (2) RC4 decryption functionality in the crypto library in MIT Kerberos 5 (aka krb5) 1.3 through 1.6.3, and 1.7 before 1.7.1, allow remote attackers to cause a denial of service (daemon crash) or possibly execute arbitrary code by providing ciphertext with a length that is too short to be valid.

Per: http://web.mit.edu/kerberos/advisories/MITKRB5-SA-2009-004.txt

"Only releases krb5-1.3 and later are vulnerable, as
earlier releases did not contain the functionality implemented by the
vulnerable code.

This is an implementation vulnerability in MIT krb5, and is not a
vulnerability in the Kerberos protocol."

Per: http://web.mit.edu/kerberos/advisories/MITKRB5-SA-2009-004.txt

FIXES
=====

* The upcoming krb5-1.7.1 and krb5-1.6.4 releases will contain a fix
for this vulnerability.

* For the krb5-1.7 release, apply the patch available at:

http://web.mit.edu/kerberos/advisories/2009-004-patch_1.7.txt

A PGP-signed patch is available at

http://web.mit.edu/kerberos/advisories/2009-004-patch_1.7.txt.asc

* For the krb5-1.6 releases, apply the patch available at:

http://web.mit.edu/kerberos/advisories/2009-004-patch_1.6.3.txt

A PGP-signed patch is available at

http://web.mit.edu/kerberos/advisories/2009-004-patch_1.6.3.txt.asc

* The krb5-1.6.3 patch might apply successfully to older releases.