Source: cve@mitre.org
Buffer overflow in HP-UX newgrp program.
HP-UX systems are vulnerable to a critical buffer overflow in the newgrp utility, allowing attackers to potentially gain unauthorized root access. This vulnerability, dating back to 1996, can lead to complete system compromise and data exfiltration if successfully exploited.
Step 1: Input Submission: The attacker crafts a malicious input string, typically a long string designed to overflow a buffer within the newgrp program.
Step 2: Program Execution: The attacker executes newgrp with the malicious input as an argument.
Step 3: Buffer Overflow: The newgrp program attempts to store the input string in a fixed-size buffer. Due to the lack of bounds checking, the oversized input overflows the buffer, overwriting adjacent memory locations on the stack.
Step 4: Control Hijacking: The overflow overwrites the return address of the function. The attacker carefully crafts the input to overwrite the return address with the address of their shellcode, or a location that will lead to their shellcode.
Step 5: Shellcode Execution: When the function returns, the program jumps to the attacker-controlled address, executing the attacker's shellcode. This shellcode typically grants the attacker a root shell or other elevated privileges.
Step 6: Privilege Escalation: The attacker now has elevated privileges, allowing them to execute arbitrary commands, access sensitive data, and potentially compromise the entire system.
The vulnerability lies within the newgrp program's handling of user input, specifically when processing arguments passed to it. The program fails to properly validate the length of the input, leading to a buffer overflow. When a specially crafted, excessively long string is provided as input, it overwrites adjacent memory regions, including the return address on the stack. By controlling the overwritten return address, an attacker can redirect program execution to arbitrary code, typically a shellcode payload, granting them elevated privileges. The root cause is a lack of bounds checking on the input buffer used to store user-supplied data. This allows an attacker to write beyond the allocated memory space, corrupting the stack and hijacking program control.
Due to the age and nature of the vulnerability, it is likely that various threat actors, including both sophisticated APTs and opportunistic attackers, could exploit this. While specific APT attribution is difficult, any actor targeting HP-UX systems would be a potential threat. CISA KEV status: Not Applicable (due to age and lack of specific KEV listing, but the vulnerability's severity warrants consideration).
Monitor system logs for unusual activity related to the newgrp command, such as excessively long command-line arguments or repeated failed login attempts.
Analyze network traffic for suspicious connections to the vulnerable system, especially those originating from untrusted sources.
Implement file integrity monitoring to detect any unauthorized modifications to the newgrp binary or related system files.
Use intrusion detection systems (IDS) with signatures specifically designed to detect buffer overflow attempts against newgrp or similar vulnerabilities.
Examine core dumps or crash logs for evidence of buffer overflows, such as stack corruption or unexpected program behavior.
Apply security patches provided by HP/Hewlett-Packard for the affected HP-UX versions. This is the most effective remediation.
If patching is not immediately feasible, restrict access to the newgrp command to only authorized users. Consider removing the setgid bit from the newgrp binary if the functionality is not required.
Implement strong input validation on any custom scripts or applications that interact with the newgrp command or user input.
Employ a host-based intrusion detection system (HIDS) to monitor for suspicious activity and alert on potential exploitation attempts.
Regularly audit system configurations and user accounts to identify and mitigate potential security risks.
Implement a defense-in-depth strategy, including network segmentation, access controls, and regular security assessments.