CVE-2000-1107 in Linux
Summary
by MITRE
in.identd ident server in SuSE Linux 6.x and 7.0 allows remote attackers to cause a denial of service via a long request, which causes the server to access a NULL pointer and crash.
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Analysis
by VulDB Data Team • 05/28/2018
The vulnerability described in CVE-2000-1107 represents a classic buffer overflow condition affecting the identd service in SuSE Linux 6.x and 7.0 systems. This flaw exists within the in.identd daemon which provides identification services for TCP connections, allowing remote attackers to exploit a malformed request that triggers a NULL pointer dereference. The identd service operates on port 113 and is commonly used by various network applications to determine the user identity associated with a particular TCP connection. When a maliciously crafted request containing an excessively long payload is sent to the service, the application fails to properly validate input length before processing, leading to memory corruption and subsequent service termination. This vulnerability specifically manifests as a denial of service condition that completely disrupts the identd service functionality.
The technical root cause of this vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and CWE-125, which covers out-of-bounds read errors. The flaw occurs because the identd implementation does not adequately validate the length of incoming requests before attempting to process them, resulting in a situation where a buffer overflow condition causes the program to access invalid memory locations. The NULL pointer dereference represents a critical memory management error where the application attempts to access memory at address zero, causing an immediate crash and system instability. This type of vulnerability is particularly dangerous in network services as it can be exploited remotely without requiring authentication, making it a prime target for automated scanning and exploitation tools.
The operational impact of CVE-2000-1107 extends beyond simple service disruption as it can affect network connectivity and system availability across multiple applications that rely on identd for user identification. Network administrators may observe intermittent service failures, particularly in environments where the identd service is used for authentication or access control purposes. The vulnerability affects systems running SuSE Linux 6.x and 7.0, which were widely deployed in enterprise environments during the late 1990s and early 2000s, making this a significant concern for organizations maintaining legacy systems. The remote exploitation capability means that attackers can trigger the denial of service condition from anywhere on the network without requiring physical access or local credentials. This vulnerability also relates to ATT&CK technique T1499.004 which covers network denial of service attacks, and T1071.004 which involves application layer protocol manipulation.
Mitigation strategies for this vulnerability include immediate patching of affected systems with updated identd implementations or system updates from SuSE that address the input validation flaws. System administrators should disable the identd service entirely if it is not required for network operations, as this eliminates the attack surface entirely. Network segmentation and firewall rules can be implemented to restrict access to port 113 from untrusted networks, limiting potential exploitation. Additionally, implementing intrusion detection systems that monitor for malformed identd requests can provide early warning of attempted exploitation. The vulnerability demonstrates the importance of proper input validation and memory management in network services, as even seemingly benign identification protocols can become critical attack vectors when insufficiently protected against malformed input. Organizations should also conduct regular vulnerability assessments to identify similar flaws in other network services and ensure proper security configurations are maintained across their infrastructure.