CVE-1999-0746 in Linux
Summary
by MITRE
A default configuration of in.identd in SuSE Linux waits 120 seconds between requests, allowing a remote attacker to conduct a denial of service.
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Analysis
by VulDB Data Team • 09/18/2024
The vulnerability identified as CVE-1999-0746 pertains to the default configuration of the in.identd service in SuSE Linux systems, representing a classic example of a denial of service weakness that exploits timing characteristics within network protocols. This flaw specifically affects the ident protocol implementation that runs on port 113, which is used by various network services to identify users connecting to systems. The in.identd service in SuSE Linux was configured to maintain a 120-second delay between processing incoming identification requests, creating a predictable and exploitable timing window that attackers could leverage for malicious purposes.
The technical implementation of this vulnerability stems from the service's design philosophy that prioritizes security through delay mechanisms, which paradoxically creates a weakness that can be weaponized. The ident protocol serves as a fundamental component in network diagnostics and authentication, where services rely on the ident response to determine user identities for logging, access control, and auditing purposes. When in.identd waits 120 seconds between requests, it creates a significant bottleneck that can be exploited by attackers who send multiple identification requests to consume available service resources and prevent legitimate users from accessing the system. This behavior aligns with CWE-400, which categorizes denial of service vulnerabilities related to resource exhaustion or timing characteristics, and specifically demonstrates how timing delays can be manipulated to create service unavailability.
The operational impact of this vulnerability extends beyond simple service disruption to encompass broader network security implications. Attackers can exploit this weakness by initiating multiple concurrent ident requests, causing the service to become unresponsive for extended periods and effectively rendering the system's identification capabilities ineffective. This creates cascading effects where dependent services that rely on ident protocol responses may also become unstable or unavailable, potentially affecting network connectivity and authentication mechanisms across the entire system. The vulnerability represents a significant concern in environments where ident protocol services are actively used for security auditing, as it allows adversaries to disrupt these critical functions while maintaining plausible deniability due to the legitimate nature of the ident protocol itself.
Mitigation strategies for this vulnerability should focus on both immediate configuration changes and broader security hardening practices. System administrators should modify the default in.identd configuration to reduce or eliminate the 120-second delay between requests, implementing more efficient request processing mechanisms that can handle multiple concurrent connections without introducing artificial delays. The recommended approach involves configuring the service to process requests immediately rather than introducing artificial timing delays that create exploitable conditions. Additionally, organizations should consider disabling the ident service entirely if it is not required for their specific network environment, following the principle of least privilege and reducing the attack surface. This vulnerability also highlights the importance of regular security auditing and configuration reviews, as it demonstrates how default security settings can inadvertently create weaknesses that align with ATT&CK technique T1499, which covers denial of service attacks through resource exhaustion or timing manipulation. The remediation process should include comprehensive testing to ensure that any changes to the ident service configuration do not negatively impact legitimate network operations while effectively addressing the identified timing vulnerability.