CVE-2000-0548 in Kerberos
Summary
by MITRE
Buffer overflow in Kerberos 4 KDC program allows remote attackers to cause a denial of service via the e_msg variable in the kerb_err_reply function.
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Analysis
by VulDB Data Team • 05/26/2018
The vulnerability described in CVE-2000-0548 represents a critical buffer overflow condition within the Kerberos 4 Key Distribution Center (KDC) implementation that fundamentally compromises system stability and availability. This flaw exists specifically within the kerb_err_reply function where the e_msg variable is processed without adequate bounds checking, creating an exploitable condition that remote attackers can leverage to disrupt services. The Kerberos 4 protocol, while now deprecated, was widely deployed in enterprise environments during the late 1990s and early 2000s, making this vulnerability particularly significant as it affected numerous critical infrastructure systems. The buffer overflow occurs when the KDC receives a malformed error message that exceeds the allocated buffer space, leading to memory corruption that can result in program termination or unpredictable behavior. This vulnerability directly maps to CWE-121, which classifies buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations, and aligns with ATT&CK technique T1499.301 which covers network denial of service attacks targeting authentication services. The operational impact extends beyond simple service disruption as the vulnerability can be exploited to cause complete system crashes, potentially requiring system restarts and manual intervention to restore normal operations. Attackers exploiting this vulnerability typically craft specially formatted error messages that trigger the buffer overflow condition, causing the KDC process to terminate unexpectedly. The lack of proper input validation in the kerb_err_reply function creates a pathway for malicious actors to inject data that overflows the e_msg buffer, potentially leading to arbitrary code execution or complete service unavailability. Organizations running Kerberos 4 implementations were particularly vulnerable because the protocol's architecture did not include robust memory protection mechanisms. The vulnerability demonstrates the critical importance of proper input validation and bounds checking in security-critical components, as even error handling routines can become attack vectors when not properly secured. This flaw underscores the necessity of defensive programming practices where all input processing, including error handling paths, must be validated against expected boundaries and lengths. The widespread adoption of Kerberos 4 in enterprise environments during this period meant that exploitation of this vulnerability could have cascading effects across multiple systems that relied on the same authentication infrastructure. Modern security frameworks would classify this as a high-risk vulnerability requiring immediate patching, though the age of this vulnerability means it primarily serves as a historical example of how inadequate input validation in core security components can lead to complete service disruption. The remediation strategy involves applying patches that implement proper bounds checking for the e_msg variable and ensuring that all input to the kerb_err_reply function is validated before processing, effectively preventing the buffer overflow condition from occurring. Organizations should also consider migrating from Kerberos 4 to more modern authentication protocols such as Kerberos 5 or alternative authentication mechanisms that have better security track records and more robust implementations.