Heimdal CVE-2017-11103 Man in the Middle Security Bypass Vulnerability

Description: Heimdal before 7.4 allows remote attackers to impersonate services with Orpheus’ Lyre attacks because it obtains service-principal names in a way that violates the Kerberos 5 protocol specification. In _krb5_extract_ticket() the KDC-REP service name must be obtained from the encrypted version stored in ‘enc_part’ instead of the unencrypted version stored in ‘ticket’. Use of the unencrypted version provides an opportunity for successful server impersonation and other attacks. NOTE: this CVE is only for Heimdal and other products that embed Heimdal code; it does not apply to other instances in which this part of the Kerberos 5 protocol specification is violated.

Impact: Successfully exploiting this issue may allow attackers to bypass certain security restrictions and perform unauthorized actions by conducting a man-in-the-middle attack. This may lead to other attacks.

Mitigation: Updates are available. Please check specific vendor advisory for more information.

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