A buffer overflow flaw was found in the MIT krb5 telnet daemon (telnetd) as shipped with all supported versions of Red Hat Enterprise Linux. A remote attacker who can access the telnet port of a target machine could use this flaw to execute arbitrary code as root.
While we are aware of public exploits for this issue that include targets for Red Hat Enterprise Linux 3, we are not aware of any yet which would be successful in gaining arbitrary root code execution in Red Hat Enterprise Linux 4, 5, or 6. However it is plausible that one could be created to do so.
Note that the krb5 telnet daemon is not enabled by default in any version of Red Hat Enterprise Linux. In addition, the default firewall rules block remote access to the telnet port. This flaw does not affect the telnet daemon distributed in the telnet-server package.
For users who have enabled the krb5 telnet daemon and have it accessible remotely, they should disable it or apply the updates we have released.
Since same encryption code is shared between the MIT krb5 telnet daemon and the telnet client, this issue affects the telnet client as well. The updates we have released fixes the issue for both, the telnet daemon and the telnet client.
Red Hat Security Errata
|Red Hat Enterprise Linux Server EUS (v. 6.1) (krb5-appl)||RHSA-2011:1854||2011-12-28|
|Red Hat Enterprise Linux 4 (krb5)||RHSA-2011:1851||2011-12-27|
|Red Hat Enterprise Linux Long Life (v. 5.3 server) (krb5)||RHSA-2011:1853||2011-12-28|
|Red Hat Enterprise Linux Server EUS (v. 6.0) (krb5-appl)||RHSA-2011:1854||2011-12-28|
|Red Hat Enterprise Linux 5 (krb5)||RHSA-2011:1851||2011-12-27|
|Red Hat Enterprise Linux EUS (v. 5.6 server) (krb5)||RHSA-2011:1853||2011-12-28|
|Red Hat Enterprise Linux 6 (krb5-appl)||RHSA-2011:1852||2011-12-27|
|Red Hat Enterprise Linux Extended Lifecycle Support 3 (krb5)||RHSA-2011:1853||2011-12-28|
Affected Packages State
|Red Hat Enterprise Linux 3||krb5||Affected|