Source: cve@mitre.org
Buffer overflow in chfn command in HP-UX 9.X through 10.20 allows local users to gain privileges via a long command line argument.
HP-UX systems running versions 9.X through 10.20 are vulnerable to a local privilege escalation attack via a buffer overflow in the chfn command. Successful exploitation allows attackers to execute arbitrary code with elevated privileges, potentially leading to complete system compromise and data exfiltration. This vulnerability, though old, remains a risk if legacy systems are still in operation and unpatched.
Step 1: Input Preparation: The attacker crafts a malicious input string, typically a long string designed to overflow the buffer allocated within the chfn command. This string includes shellcode and overwrites the return address on the stack.
Step 2: Command Execution: The attacker executes the chfn command with the crafted malicious input as a command-line argument.
Step 3: Buffer Overflow: The chfn command processes the input, and due to the lack of bounds checking, the long input overflows the allocated buffer.
Step 4: Control Hijack: The overflow overwrites the return address on the stack with the address of the attacker's shellcode.
Step 5: Shellcode Execution: When the chfn command attempts to return, it jumps to the attacker's shellcode, which executes with the privileges of the user running chfn (potentially root).
The vulnerability lies within the chfn command's handling of command-line arguments. Specifically, the program fails to properly validate the size of user-supplied input, leading to a buffer overflow. When a long string is provided as an argument, it overwrites adjacent memory regions, including the stack. By carefully crafting the input, an attacker can overwrite critical data, such as the return address, and redirect program execution to malicious code (e.g., a shellcode) placed within the overflowed buffer. The lack of bounds checking on input, coupled with the execution of the attacker-controlled code, results in the attacker gaining the privileges of the user running the chfn command, which is often a privileged user like root.
This vulnerability is not directly associated with specific APT groups or malware campaigns in recent years due to its age. However, it could be incorporated into a larger attack chain targeting vulnerable legacy systems. Not listed on CISA KEV.
Monitor system logs for unusually long command-line arguments passed to the chfn command.
Analyze system logs for suspicious activity following execution of the chfn command, such as the creation of new user accounts or changes to system files.
Implement file integrity monitoring to detect unauthorized modifications to system binaries or configuration files.
Network intrusion detection systems (IDS) might detect unusual network traffic originating from the compromised system, especially if the attacker attempts to establish a reverse shell or exfiltrate data.
Upgrade to a patched version of HP-UX (11.00 or later) or apply the vendor-provided security patches for the affected versions.
Implement least privilege principles, limiting the permissions of users and processes.
Regularly audit system configurations and user accounts to identify and remediate potential security weaknesses.
Implement strong input validation to prevent buffer overflows and other vulnerabilities.
Use a host-based intrusion detection system (HIDS) to monitor for malicious activity.
Disable the chfn command if it is not required for normal system operation.