CVE-2003-0059 in Kerberos
Summary
by MITRE
Unknown vulnerability in the chk_trans.c of the libkrb5 library for MIT Kerberos V5 before 1.2.5 allows users from one realm to impersonate users in other realms that have the same inter-realm keys.
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Analysis
by VulDB Data Team • 08/25/2025
The vulnerability described in CVE-2003-0059 represents a critical security flaw within the MIT Kerberos V5 implementation that affects the chk_trans.c component of the libkrb5 library. This issue specifically targets the inter-realm authentication mechanism that enables secure communication between different Kerberos realms. The vulnerability exists in versions prior to 1.2.5 and fundamentally undermines the security model that Kerberos employs to maintain trust boundaries between separate authentication domains. The flaw allows malicious actors to exploit weaknesses in the realm-to-realm trust validation process, creating a scenario where users from one realm can potentially masquerade as legitimate users from another realm.
The technical nature of this vulnerability stems from insufficient validation of inter-realm trust relationships within the Kerberos authentication framework. When two Kerberos realms share the same inter-realm key, the system should enforce strict validation mechanisms to ensure that authentication requests originate from legitimate sources within the trusted realm. However, the chk_trans.c implementation failed to properly verify the authenticity of cross-realm authentication requests, allowing attackers to craft malicious authentication tokens that could be accepted by the target realm. This represents a failure in the cryptographic validation process that should prevent unauthorized impersonation across trust boundaries.
The operational impact of this vulnerability extends far beyond simple authentication bypass, as it fundamentally compromises the integrity of cross-realm trust relationships that are essential for large-scale enterprise and academic environments. Organizations that rely on multiple Kerberos realms for different departments, subsidiaries, or geographical locations become vulnerable to lateral movement attacks where an attacker in one realm can escalate privileges and gain unauthorized access to resources in other realms. The vulnerability affects the core security principle of Kerberos that relies on trusted relationships between realms, potentially allowing attackers to access sensitive data, escalate privileges, and perform unauthorized operations across multiple trusted domains within the same organization. This type of vulnerability directly impacts the confidentiality, integrity, and availability of the entire Kerberos infrastructure.
The vulnerability aligns with CWE-287 which addresses improper authentication issues in security systems, and represents a significant weakness in the authentication delegation model. From an ATT&CK perspective, this vulnerability maps to techniques involving privilege escalation and lateral movement, as attackers can leverage the impersonation capability to move between different security domains within the same organization. Organizations should immediately implement patch management procedures to upgrade to MIT Kerberos V5 version 1.2.5 or later, which contains the necessary fixes for the inter-realm trust validation. Additionally, administrators should review existing inter-realm key configurations and implement additional monitoring of authentication logs to detect potential exploitation attempts. Network segmentation and additional authentication controls should be considered as temporary mitigations while full patch deployment occurs. The vulnerability demonstrates the critical importance of maintaining up-to-date security implementations and proper validation of trust relationships in distributed authentication systems.