CVE-1999-0048 in AIX
Summary
by MITRE
Talkd, when given corrupt DNS information, can be used to execute arbitrary commands with root privileges.
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Analysis
by VulDB Data Team • 04/16/2026
The vulnerability identified as CVE-1999-0048 affects the talkd daemon, a network service that facilitates communication between users on different systems. This daemon operates on TCP port 517 and is part of the traditional unix communication utilities. The flaw manifests when the talkd service receives malformed or corrupt DNS information during its operation, creating a condition where malicious actors can exploit the service to execute arbitrary commands with elevated privileges. This represents a classic privilege escalation vulnerability that leverages network service misconfigurations to gain system-level access.
The technical root cause of this vulnerability lies in the insecure handling of DNS responses within the talkd implementation. When the daemon attempts to resolve hostnames for communication purposes, it does not properly validate or sanitize the DNS data it receives. This lack of input validation creates a path for attackers to inject malicious data that can be interpreted as executable commands. The vulnerability operates under CWE-20, which describes improper input validation, and more specifically aligns with CWE-78, which addresses OS command injection. The flaw demonstrates a dangerous combination of network service interaction and command execution that bypasses normal privilege boundaries.
The operational impact of CVE-1999-0048 is severe as it allows remote attackers to gain root access to systems running vulnerable versions of talkd. This privilege escalation capability means that an attacker could execute commands with the highest system privileges, potentially leading to complete system compromise. The vulnerability is particularly dangerous because it requires no authentication to exploit, making it accessible to anyone who can reach the talkd service over the network. This aligns with ATT&CK technique T1068, which covers exploitation of remote services for privilege escalation, and T1072, which involves the use of remote services to establish persistent access.
Systems affected by this vulnerability typically include older unix-like operating systems that still ship with the talkd daemon, particularly those running versions of the operating system predating security hardening practices. The vulnerability is especially prevalent on systems that have not received security updates or have not disabled the talkd service entirely. Organizations running these services without proper network segmentation or firewall rules are particularly at risk, as the vulnerability can be exploited from any network location where the service is accessible. Mitigation strategies should include immediate disabling of the talkd service, network segmentation to restrict access to the service, and implementation of proper DNS validation mechanisms to prevent the injection of malicious data. The vulnerability also highlights the importance of proper input validation in network services and demonstrates how seemingly innocuous service interactions can create significant security risks when proper sanitization procedures are not implemented.