CVE-1999-1075 in AIX
Summary
by MITRE
inetd in AIX 4.1.5 dynamically assigns a port N when starting ttdbserver (ToolTalk server), but also inadvertently listens on port N-1 without passing control to ttdbserver, which allows remote attackers to cause a denial of service via a large number of connections to port N-1, which are not properly closed by inetd.
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Analysis
by VulDB Data Team • 04/17/2026
The vulnerability described in CVE-1999-1075 represents a significant denial of service weakness in the inetd service management framework of IBM AIX 4.1.5 systems. This issue stems from the improper handling of port assignment and service delegation during the startup process of the tooltalk server component. The inetd daemon, which serves as a super-server for managing network services, exhibits flawed behavior when initializing the ttdbserver process by dynamically selecting a port number for service exposure.
The technical flaw manifests when inetd assigns a specific port number n to the ttdbserver process while simultaneously maintaining listening status on port n-1 without properly transferring control to the newly launched server. This dual listening condition creates an exploitable scenario where malicious actors can target the uncontrolled port n-1 with a high volume of connection attempts. The vulnerability is classified under CWE-643 as an improper neutralization of data within a command, specifically concerning the improper handling of service initialization parameters. The root cause lies in the lack of proper port management protocols during service startup, creating an unintended listening socket that remains unmanaged by the intended server process.
From an operational impact perspective, this vulnerability allows remote attackers to effectively perform a denial of service attack against the affected AIX system by overwhelming port n-1 with connection requests. The inetd daemon fails to properly close or manage these connections, leading to resource exhaustion and service disruption. The attack vector is particularly effective because it targets a port that should normally be controlled by the ttdbserver process but remains accessible through the inetd service. This creates a persistent attack surface that can be exploited without requiring authentication or elevated privileges, making it particularly dangerous in production environments where service availability is critical. The vulnerability aligns with ATT&CK technique T1499.004 for network denial of service attacks, specifically targeting service availability through connection flooding.
The mitigation strategies for this vulnerability should focus on immediate system hardening measures and proper service management protocols. System administrators should ensure that all services are properly configured with explicit port assignments and that inetd does not maintain unnecessary listening sockets. The recommended approach involves either patching the AIX system to correct the port assignment logic or implementing proper service delegation mechanisms that prevent the dual listening condition. Additionally, network-level protections such as firewall rules can be implemented to restrict access to the vulnerable port n-1 while the system remains unpatched. The vulnerability demonstrates the critical importance of proper service initialization procedures and the potential for seemingly minor configuration issues to create significant security weaknesses that can be exploited for denial of service attacks.