CVE-1999-0090 in AIX
Summary
by MITRE
buffer overflow in aix rcp command allows local users to obtain root access.
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Analysis
by VulDB Data Team • 04/17/2026
The vulnerability described in CVE-1999-0090 represents a critical buffer overflow flaw within the rcp command on IBM AIX operating systems. This issue affects the remote copy utility that is part of the standard AIX distribution and enables local users to exploit a memory corruption vulnerability that can be leveraged to escalate privileges to root access. The rcp command is used for copying files between systems and typically operates with elevated privileges during its execution, making it a prime target for privilege escalation attacks. This vulnerability specifically resides in the command line argument parsing mechanism of the rcp utility where insufficient bounds checking allows attackers to overflow a fixed-size buffer, potentially leading to arbitrary code execution with root privileges.
The technical implementation of this buffer overflow occurs when the rcp command processes command line arguments without adequate validation of input length. When a local user provides an excessively long argument string to the rcp command, the program fails to properly check the buffer boundaries, resulting in memory corruption that can overwrite adjacent memory locations including return addresses on the stack. This type of vulnerability falls under the CWE-121 category of stack-based buffer overflow, which is classified as a common weakness in software development practices. The flaw is particularly dangerous because the rcp command typically runs with elevated privileges, and the overflow can be manipulated to overwrite the return address, allowing an attacker to redirect program execution flow and execute malicious code with root permissions.
From an operational perspective, this vulnerability presents a significant risk to AIX systems that have the rcp command installed and accessible to local users. The local privilege escalation aspect means that even users with minimal system access can potentially gain complete administrative control over the affected systems. Attackers can exploit this vulnerability by crafting specific command line arguments that cause the buffer overflow, then using the corrupted execution flow to inject and execute malicious code. The attack vector is particularly concerning because it requires no network connectivity or remote access, making it a local attack that can be executed from within the system itself. The vulnerability impacts all versions of AIX that include the vulnerable rcp implementation and can be exploited across multiple AIX releases from version 4.1 through 5.1, according to the original vulnerability reports. This makes the attack surface particularly broad across the AIX ecosystem.
The mitigation strategies for this vulnerability include immediate patching of the affected AIX systems with the appropriate security fixes provided by IBM, which typically involve correcting the buffer handling in the rcp command implementation. Organizations should also implement proper input validation and bounds checking in all system utilities, following secure coding practices that prevent buffer overflow conditions. Additionally, system administrators should disable unnecessary network services and utilities, particularly those that run with elevated privileges, to reduce the attack surface. The vulnerability demonstrates the importance of the principle of least privilege, where system utilities should only operate with the minimum necessary permissions. Security monitoring should be enhanced to detect unusual command line arguments or execution patterns that might indicate exploitation attempts. This vulnerability also highlights the need for regular security assessments and code reviews to identify similar buffer overflow conditions in other system utilities. The attack pattern aligns with the MITRE ATT&CK framework under privilege escalation techniques, specifically targeting local persistence and privilege escalation through system binary manipulation. Organizations should maintain comprehensive patch management processes to ensure timely deployment of security fixes for known vulnerabilities in system utilities and core operating system components.