CVE-2000-0547 in Kerberos
Summary
by MITRE
Buffer overflow in Kerberos 4 KDC program allows remote attackers to cause a denial of service via the localrealm variable in the process_v4 function.
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Analysis
by VulDB Data Team • 05/26/2018
The vulnerability identified as CVE-2000-0547 represents a critical buffer overflow flaw within the Kerberos 4 Key Distribution Center implementation that fundamentally compromises system availability. This weakness resides in the process_v4 function where the localrealm variable handling creates an exploitable condition that remote attackers can leverage to execute denial of service attacks against Kerberos services. The vulnerability specifically targets the Kerberos 4 protocol implementation that was widely deployed in enterprise environments during the late 1990s and early 2000s, making it particularly significant given the protocol's widespread adoption for network authentication. The buffer overflow occurs when the KDC processes authentication requests containing malformed realm information, leading to unpredictable program behavior and system instability.
The technical exploitation of this vulnerability stems from inadequate input validation within the Kerberos 4 KDC software where the localrealm parameter is processed without proper bounds checking. When an attacker sends a specially crafted authentication request containing excessive data in the realm field, the program attempts to copy this data into a fixed-size buffer without verifying that the input length exceeds the allocated space. This classic buffer overflow condition allows attackers to overwrite adjacent memory locations, potentially causing the KDC process to crash or behave unpredictably. The flaw falls under CWE-121 which categorizes buffer overflow conditions where insufficient bounds checking permits data to be written beyond the allocated buffer boundaries, directly violating fundamental security principles of memory safety.
The operational impact of CVE-2000-0547 extends beyond simple service disruption to encompass broader security implications within network authentication infrastructure. Organizations relying on Kerberos 4 for authentication services face potential complete service outages when attackers exploit this vulnerability, as the KDC process failure effectively prevents legitimate users from authenticating to network resources. This denial of service condition can be particularly devastating in enterprise environments where Kerberos serves as a foundational authentication mechanism for critical services, potentially leading to cascading failures across dependent systems. The vulnerability's remote exploitability means attackers need not be physically present on the network, enabling widespread disruption from any location with network access to the affected KDC services. According to ATT&CK framework tactic T1499, this represents a denial of service attack that targets network services and can be classified under the broader category of availability attacks.
Mitigation strategies for CVE-2000-0547 require immediate implementation of software patches provided by vendors, as the vulnerability cannot be effectively addressed through configuration changes alone. Organizations should prioritize upgrading to patched versions of Kerberos 4 implementations or migrating to more modern authentication protocols such as Kerberos 5 or alternative authentication mechanisms that have addressed these buffer overflow vulnerabilities. Network segmentation and access controls should be implemented to limit exposure of KDC services to untrusted networks, while monitoring systems should be deployed to detect anomalous authentication requests that might indicate exploitation attempts. The vulnerability's age and the availability of comprehensive patches make migration from legacy Kerberos 4 implementations a recommended long-term solution, as this protocol version contains multiple security weaknesses that have been addressed in subsequent releases. Security teams should also implement intrusion detection systems capable of identifying patterns associated with buffer overflow exploitation attempts, particularly focusing on malformed realm parameters in authentication requests.