(RHSA-2010:0925) Important: krb5 security and bug fix update

Kerberos is a network authentication system which allows clients and
servers to authenticate to each other using symmetric encryption and a
trusted third party, the Key Distribution Center (KDC).

Multiple checksum validation flaws were discovered in the MIT Kerberos
implementation. A remote attacker could use these flaws to tamper with
certain Kerberos protocol packets and, possibly, bypass authentication or
authorization mechanisms and escalate their privileges. (CVE-2010-1323,
CVE-2010-1324, CVE-2010-4020)

Red Hat would like to thank the MIT Kerberos Team for reporting these
issues.

This update also fixes the following bug:

• When attempting to perform PKINIT pre-authentication, if the client had
  more than one possible candidate certificate the client could fail to
  select the certificate and key to use. This usually occurred if certificate
  selection was configured to use the value of the keyUsage extension, or if
  any of the candidate certificates did not contain a subjectAltName
  extension. Consequently, the client attempted to perform pre-authentication
  using a different (usually password-based) mechanism. (BZ#644825)

All krb5 users should upgrade to these updated packages, which contain
backported patches to correct these issues. After installing the updated
packages, the krb5kdc daemon will be restarted automatically.