CVE-2000-0867 in Linux
Summary
by MITRE
Kernel logging daemon (klogd) in Linux does not properly cleanse user-injected format strings, which allows local users to gain root privileges by triggering malformed kernel messages.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 05/17/2018
The vulnerability identified as CVE-2000-0867 resides within the Linux kernel logging daemon known as klogd which operates with elevated privileges to process and log kernel messages. This daemon serves as a critical component in the Linux kernel's logging infrastructure, responsible for reading kernel messages from the kernel ring buffer and forwarding them to the system log daemon syslogd. The flaw manifests when klogd encounters malformed kernel messages containing format strings that are not properly sanitized before being processed. This vulnerability represents a classic buffer overflow and format string exploitation vector that has been documented in various security literature and aligns with CWE-134 which specifically addresses the use of untrusted data in format string functions. The vulnerability operates under the principle that when klogd processes kernel messages containing format specifiers such as %s, %d, or %x without proper validation, it can be manipulated to execute arbitrary code with root privileges.
The technical exploitation of this vulnerability occurs when a local attacker crafts malicious kernel messages that contain specially formatted strings designed to trigger the format string vulnerability within klogd. This typically involves creating kernel modules or using kernel debugging interfaces that generate kernel messages containing format specifiers that reference memory locations. When klogd processes these messages, it interprets the format specifiers as instructions to read from or write to specific memory addresses, potentially allowing an attacker to overwrite critical function pointers or execute arbitrary code. The attack vector leverages the fact that klogd runs with root privileges and has access to kernel message buffers that can be manipulated by local users. This vulnerability falls under the ATT&CK technique T1068 which describes 'Exploitation for Privilege Escalation' and specifically targets the 'Exploitation for Privilege Escalation' tactic within the MITRE ATT&CK framework. The exploitation process typically involves multiple stages including kernel message generation, format string manipulation, and memory corruption to achieve privilege escalation.
The operational impact of CVE-2000-0867 is significant as it allows local users to escalate their privileges from regular user level to root access without requiring any special authentication or network connectivity. This makes the vulnerability particularly dangerous in multi-user environments where local access is possible, as it can be exploited by malicious users or attackers who have gained access to a system through other means. The vulnerability affects all versions of Linux kernel logging daemon that do not properly implement format string validation, making it a widespread issue across many Linux distributions of that era. Once exploited, the attacker gains complete control over the system, enabling them to modify system files, install backdoors, steal sensitive information, or disrupt system operations. The vulnerability also demonstrates a fundamental security flaw in how kernel logging systems handle untrusted input, highlighting the importance of input validation and sanitization in security-critical components. Organizations running vulnerable systems face potential data breaches, system compromise, and complete loss of system integrity, as the exploitation can be performed without detection.
Mitigation strategies for CVE-2000-0867 focus on both immediate patching and operational security measures. The primary solution involves updating to patched versions of the Linux kernel and klogd where proper format string validation has been implemented. This typically requires system administrators to apply security patches from their distribution vendors or compile updated kernel sources with proper input sanitization. Additionally, system administrators should consider running klogd with reduced privileges or implementing process isolation to limit the impact of potential exploitation. The vulnerability also emphasizes the importance of least privilege principles and proper system hardening, ensuring that security-critical daemons do not run with unnecessary elevated privileges. Organizations should implement monitoring and alerting for unusual kernel message patterns that might indicate exploitation attempts. Network segmentation and access controls should be employed to limit local access to systems where possible, reducing the attack surface. The remediation process should also include comprehensive security audits to identify other potential format string vulnerabilities in similar system components and ensure proper input validation practices are implemented across the entire system architecture. System administrators should also consider implementing intrusion detection systems that can monitor for suspicious kernel message patterns or attempts to exploit similar vulnerabilities in the kernel logging infrastructure.