CVE-2000-0391 in Kerberos
Summary
by MITRE
Buffer overflow in krshd in Kerberos 5 allows remote attackers to gain root privileges.
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Analysis
by VulDB Data Team • 04/21/2026
The vulnerability identified as CVE-2000-0391 represents a critical buffer overflow flaw within the krshd component of Kerberos 5 authentication system. This issue exists in the remote shell daemon implementation that handles secure remote command execution through the Kerberos authentication framework. The buffer overflow vulnerability specifically manifests when krshd processes incoming network data from remote clients without proper bounds checking, allowing malicious input to overwrite adjacent memory locations beyond the allocated buffer space.
This technical flaw directly relates to CWE-121, which categorizes buffer overflow conditions where insufficient boundary checking allows attackers to overwrite adjacent memory regions. The vulnerability is particularly dangerous because it operates within the Kerberos authentication system, which serves as a foundational security component for many enterprise networks. When exploited, the buffer overflow enables remote attackers to execute arbitrary code with the privileges of the krshd process, which typically runs with root or administrator privileges on the target system.
The operational impact of CVE-2000-0391 extends beyond simple privilege escalation, as it provides attackers with complete system compromise capabilities through the Kerberos infrastructure. Attackers can leverage this vulnerability to establish persistent backdoors, exfiltrate sensitive data, or use the compromised system as a launch point for further network infiltration. The attack vector requires only network access to the vulnerable krshd service, making it particularly attractive to remote threat actors who can exploit the vulnerability without physical access to the target system. This vulnerability directly maps to ATT&CK technique T1075 which involves using legitimate credentials and remote services to gain access to systems.
The exploitation of this vulnerability typically involves crafting malicious input that exceeds the buffer capacity, causing memory corruption that can be manipulated to redirect program execution flow. Security researchers have documented various attack patterns where attackers construct specific payloads that overwrite return addresses and function pointers within the krshd process memory space. Organizations using Kerberos 5 implementations that include the krshd service were particularly vulnerable, especially those with default installations or systems that had not applied security patches. The vulnerability's severity classification as critical reflects its potential for widespread compromise across enterprise networks that rely on Kerberos for authentication services. Mitigation strategies include immediate patching of the Kerberos 5 implementation, disabling the krshd service when not required, and implementing network segmentation to limit exposure of vulnerable systems. Additionally, security monitoring should focus on unusual network connections to Kerberos services and anomalous authentication patterns that might indicate exploitation attempts.