The MIT Kerberos
krb524d daemon does not securely deallocate heap memory when handling an error condition, resulting in a double-free vulnerability. An unauthenticated, remote attacker could execute arbitrary code on a system running
krb524d, which in many cases is also a Kerberos Distribution Center (KDC). The compromise of a KDC system can lead to the compromise of an entire Kerberos realm. An attacker may also be able to cause a denial of service on a system running
As described on the MIT Kerberos web site: "Kerberos is a network authentication protocol. It is designed to provide strong authentication for client/server applications by using secret-key cryptography." MIT Kerberos code is used in network applications from a variety of different vendors and is included in many UNIX and Linux distributions.
The MIT Kerberos
krb524d daemon converts Kerberos 5 service tickets into Kerberos 4 service tickets. There is a double-free vulnerability in
krb524d that can be triggered during the conversion of a cross-realm ticket. From MITKRB5-SA-2004-002:
The patch (introduced in krb5-1.2.8 and present in all subsequent
releases) for disabling krb4 cross-realm authentication in krb524d
introduced a double-free vulnerability. If handle_classic_v4() denies
the conversion of a cross-realm ticket, v5tkt->enc_part2 gets freed
but not nulled, so do_connection() double-frees many things when it
subsequently calls krb5_free_ticket().
An unauthenticated, remote attacker to could execute arbitrary code on a system running
krb524d. In many cases, this system also operates a KDC, so this vulnerability could allow an attacker to gain the master secret for a Kerberos realm, leading to compromise of the entire realm. An attacker may also be able to crash a system running
krb524d, causing a denial of service.
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