Kerberos is a network authentication system which allows clients andservers to authenticate to each other using symmetric encryption and atrusted third party, the Key Distribution Center (KDC). The GenericSecurity Service Application Program Interface (GSS-API) definitionprovides security services to callers (protocols) in a generic fashion. TheSimple and Protected GSS-API Negotiation (SPNEGO) mechanism is used byGSS-API peers to choose from a common set of security mechanisms.An input validation flaw was found in the ASN.1 (Abstract Syntax NotationOne) decoder used by MIT Kerberos. A remote attacker could use this flaw tocrash a network service using the MIT Kerberos library, such as kadmind orkrb5kdc, by causing it to dereference or free an uninitialized pointer.(CVE-2009-0846)Multiple input validation flaws were found in the MIT Kerberos GSS-APIlibrary's implementation of the SPNEGO mechanism. A remote attacker coulduse these flaws to crash any network service utilizing the MIT KerberosGSS-API library to authenticate users or, possibly, leak portions of theservice's memory. (CVE-2009-0844, CVE-2009-0845)All krb5 users should upgrade to these updated packages, which containbackported patches to correct these issues. All running services using theMIT Kerberos libraries must be restarted for the update to take effect.