Secunia

Some vulnerabilities have been reported in Kerberos, which can be exploited by malicious users to cause a DoS or compromise a vulnerable system and by malicious people to bypass certain security restrictions.

1) An error exists in the MIT krb5 telnet daemon (telnetd) when processing the username. This can be exploited to log in as an arbitrary user by providing a specially crafted username beginning with "-e".

NOTE: If the telnet daemon is configured to only permit authenticated login, only authenticated users can exploit this vulnerability.

2) A boundary error exists in the "krb5_klog_syslog()" function within the kadm5 library, which is used by KDC, kadmind and probably other third party products. This can be exploited to cause a stack-based buffer overflow via an overly long string.

Successful exploitation allows execution of arbitrary code, but requires valid credentials.

3) A double-free error exists in the "kg_unseal_v1()" function within the MIT krb5 GSS-API library, which is used by kadmind and probably other third-party products. This can potentially be exploited to execute arbitrary code, but requires valid credentials.

The vulnerabilities are reported in version krb5-1.6. Other versions may also be affected.

Solution
Apply patches (see vendor advisories for details).
Further details available in Customer Area

Provided and/or discovered by
1, 3) Reported by the vendor
2) An anonymous person, reported via iDefense Labs

Original Advisory
Kerberos:
http://web.mit.edu/kerberos/www/advisories/MITKRB5-SA-2007-001-telnetd.txt
http://web.mit.edu/kerberos/www/advisories/MITKRB5-SA-2007-002-syslog.txt
http://web.mit.edu/kerberos/www/advisories/MITKRB5-SA-2007-003.txt

iDefense Labs:
http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=500

Other references
Further details available in Customer Area

Deep Links
Links available in Customer Area