CVE-1999-0085 in AIX
Summary
by MITRE
buffer overflow in rwhod on aix and other operating systems allows remote attackers to execute arbitrary code via a udp packet with a long hostname.
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Analysis
by VulDB Data Team • 04/03/2025
The vulnerability described in CVE-1999-0085 represents a classic buffer overflow condition affecting the rwhod daemon on AIX and similar operating systems. This daemon serves the purpose of distributing information about remote hosts and their users, operating as a UDP service that listens for requests from other systems. The flaw occurs when processing incoming UDP packets containing hostnames, where the system fails to properly validate the length of the hostname data before copying it into a fixed-size buffer. This buffer overflow condition creates a situation where an attacker can overwrite adjacent memory locations, potentially leading to arbitrary code execution with the privileges of the rwhod process. The vulnerability is particularly concerning because it operates over UDP, making it accessible to remote attackers without requiring authentication or prior system access. The affected systems include AIX operating systems and other Unix variants that implement the rwhod service, which was commonly used for network monitoring and user information distribution across local networks. This type of vulnerability falls under CWE-121, which specifically addresses buffer overflow conditions where insufficient bounds checking allows data to be written beyond allocated buffer boundaries.
The technical exploitation of this vulnerability requires an attacker to send a specially crafted UDP packet containing an excessively long hostname string to the target system's rwhod service. When the daemon processes this packet, the malformed hostname data exceeds the allocated buffer size, causing memory corruption that can be leveraged to redirect program execution flow. The attack vector operates entirely over the network without requiring any user interaction or authentication, making it particularly dangerous for systems that expose the rwhod service to untrusted networks. The operational impact extends beyond simple code execution, as successful exploitation could allow attackers to gain elevated privileges, establish persistent access, or even compromise the entire system. The vulnerability demonstrates poor input validation practices and highlights the importance of implementing proper bounds checking in network services. According to ATT&CK framework, this vulnerability maps to T1068, which covers 'Exploitation for Privilege Escalation', and T1210, which addresses 'Exploitation of Remote Services', as the attack exploits a service running on the target system to gain unauthorized access.
Mitigation strategies for CVE-1999-0085 should focus on both immediate remediation and long-term architectural improvements. The most effective immediate solution involves disabling or removing the rwhod service from systems where it is not absolutely required, as this service is largely obsolete in modern network environments. System administrators should also implement network segmentation to prevent unauthorized access to systems running rwhod services, using firewalls to block UDP traffic on the specific port used by rwhod. Additionally, applying vendor-specific patches and updates that correct the buffer overflow condition through proper input validation and bounds checking is essential. Organizations should consider implementing intrusion detection systems that can identify and alert on suspicious UDP traffic patterns that might indicate exploitation attempts. The vulnerability also underscores the importance of regular security assessments and vulnerability scanning to identify legacy services that may present similar risks. From a compliance perspective, this vulnerability relates to security standards such as NIST SP 800-53 controls that emphasize the need for secure coding practices and input validation to prevent buffer overflow exploits. Modern security practices recommend implementing stack canaries, address space layout randomization, and other exploit mitigation techniques to reduce the effectiveness of buffer overflow attacks, although these measures were not commonly available in 1999 when this vulnerability was first identified.