CVE-2000-1040 in Linux
Summary
by MITRE
Format string vulnerability in logging function of ypbind 3.3, while running in debug mode, leaks file descriptors and allows an attacker to cause a denial of service.
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Analysis
by VulDB Data Team • 05/16/2019
The vulnerability identified as CVE-2000-1040 represents a critical format string flaw within the ypbind service version 3.3, specifically manifesting during debug operations. This issue resides in the logging function implementation where improper handling of format strings creates opportunities for malicious input manipulation. The ypbind service, which is responsible for binding NIS (Network Information Service) clients to NIS servers, becomes susceptible to exploitation when operating in debug mode, a configuration typically used for troubleshooting and development purposes.
The technical flaw stems from the application's failure to properly validate and sanitize user-supplied input before using it in printf-style logging functions. When ypbind operates in debug mode, it processes incoming requests with insufficient input validation, allowing attackers to inject format specifiers that can be interpreted by the logging function. This vulnerability creates a path for information disclosure through file descriptor leakage, where the format string manipulation can expose sensitive memory contents including file descriptors, process identifiers, and potentially other system information. The improper handling of format strings directly aligns with CWE-134, which specifically addresses the use of format strings with user-supplied data without proper validation.
The operational impact of this vulnerability extends beyond simple information disclosure, as it enables remote attackers to cause a denial of service condition within the NIS infrastructure. By carefully crafting malicious input that exploits the format string vulnerability, an attacker can manipulate the logging function to cause ypbind to crash or behave unpredictably, effectively disrupting network services that depend on NIS for name resolution and authentication. This denial of service attack can have cascading effects throughout the network, as NIS is commonly used for centralized user and host information management in Unix-based systems. The vulnerability particularly affects systems where ypbind is configured to run in debug mode, which may be present in development environments or improperly secured production systems.
Mitigation strategies for CVE-2000-1040 require immediate attention from system administrators and security teams. The most effective immediate solution involves disabling debug mode operation for ypbind services unless absolutely necessary for troubleshooting purposes. Additionally, system administrators should ensure that ypbind is running with minimal privileges and that access controls are properly configured to limit who can interact with the service. The vulnerability demonstrates the importance of input validation and proper format string handling, principles that align with ATT&CK technique T1059.007 for command and scripting interpreter and T1105 for remote file copy. Organizations should implement regular security assessments to identify services running in debug mode and ensure that all applications properly sanitize input before processing, particularly in logging and output functions. The remediation process should also include updating to patched versions of ypbind if available, though this particular vulnerability predates many modern security practices, making the operational controls more critical for protection.