RHEL 7 : krb5 (RHSA-2015:2154)
Medium Nessus Plugin ID 86933
SynopsisThe remote Red Hat host is missing one or more security updates.
DescriptionUpdated krb5 packages that fix two security issues, several bugs, and add various enhancements are now available for Red Hat Enterprise Linux 7.
Red Hat Product Security has rated this update as having Moderate security impact. Common Vulnerability Scoring System (CVSS) base scores, which give detailed severity ratings, are available for each vulnerability from the CVE links in the References section.
Kerberos is a network authentication system, which can improve the security of your network by eliminating the insecure practice of sending passwords over the network in unencrypted form. It allows clients and servers to authenticate to each other with the help of a trusted third party, the Kerberos key distribution center (KDC).
It was found that the krb5_read_message() function of MIT Kerberos did not correctly sanitize input, and could create invalid krb5_data objects. A remote, unauthenticated attacker could use this flaw to crash a Kerberos child process via a specially crafted request.
A flaw was found in the OTP kdcpreauth module of MIT kerberos. An unauthenticated remote attacker could use this flaw to bypass the requires_preauth flag on a client principal and obtain a ciphertext encrypted in the principal's long-term key. This ciphertext could be used to conduct an off-line dictionary attack against the user's password. (CVE-2015-2694)
The krb5 packages have been upgraded to upstream version 1.13.2, which provides a number of bug fixes and enhancements over the previous version. (BZ#1203889)
Notably, this update fixes the following bugs :
* Previously, the RADIUS support (libkrad) in krb5 was sending krb5 authentication for Transmission Control Protocol (TCP) transports multiple times, accidentally using a code path intended to be used only for unreliable transport types, for example User Datagram Protocol (UDP) transports. A patch that fixes the problem by disabling manual retries for reliable transports, such as TCP, has been applied, and the correct code path is now used in this situation. (BZ#1251586)
* Attempts to use Kerberos single sign-on (SSO) to access SAP NetWeaver systems sometimes failed. The SAP NetWeaver developer trace displayed the following error message :
No credentials were supplied, or the credentials were unavailable or inaccessible Unable to establish the security context
Querying SSO credential lifetime has been modified to trigger credential acquisition, thus preventing the error from occurring. Now, the user can successfully use Kerberos SSO for accessing SAP NetWeaver systems. (BZ#1252454)
All krb5 users are advised to upgrade to these updated packages, which correct these issues and add these enhancements.
SolutionUpdate the affected packages.