Source: cve@mitre.org
Buffer overflow in certain RPC routines in IBM AIX 4.3 may allow attackers to execute arbitrary code, related to a "variable data type."
IBM AIX 4.3 systems are vulnerable to a remote code execution exploit due to a buffer overflow in RPC routines. Successful exploitation allows attackers to execute arbitrary code with the privileges of the vulnerable service, potentially leading to complete system compromise and data exfiltration. This vulnerability, though old, could still be present in legacy systems and requires immediate attention.
Step 1: Target Identification: The attacker identifies a vulnerable AIX 4.3 system with RPC services exposed. This can be achieved through port scanning (e.g., using nmap) or vulnerability scanning tools.
Step 2: Payload Crafting: The attacker crafts a malicious RPC request. This request includes a payload designed to trigger the buffer overflow. The payload contains the malicious code (shellcode) and data to overwrite the buffer and control flow.
Step 3: Request Delivery: The attacker sends the crafted RPC request to the vulnerable AIX 4.3 system. The request targets the specific RPC routine containing the vulnerability.
Step 4: Buffer Overflow: The vulnerable RPC routine receives the malicious request and attempts to process the data. Due to the lack of bounds checking, the data overflows the allocated buffer.
Step 5: Code Execution: The buffer overflow overwrites critical memory areas, such as function pointers. When the vulnerable routine attempts to use the overwritten pointer, it executes the attacker's injected shellcode, granting the attacker control of the system.
The vulnerability stems from a buffer overflow within RPC routines handling a "variable data type" in IBM AIX 4.3. The specific function responsible likely fails to properly validate the size of data received from a remote client before copying it into a fixed-size buffer. This lack of bounds checking allows an attacker to send a specially crafted RPC request containing data larger than the allocated buffer. This overwrites adjacent memory, potentially including critical data like function pointers or control structures. By carefully crafting the overflow, an attacker can overwrite these pointers with addresses pointing to malicious code (e.g., shellcode) injected into the overflowed buffer. When the vulnerable function attempts to use the overwritten pointer, it executes the attacker's code, granting them control of the system.
Due to the age of the vulnerability, it's unlikely to be actively targeted by sophisticated APTs. However, opportunistic attackers and script kiddies might leverage existing PoCs. The vulnerability is not listed in the CISA KEV database, reflecting its age and the likely limited number of affected systems.
Network traffic analysis: Examine network traffic for unusual RPC requests, especially those with large data payloads, targeting RPC ports (e.g., port 111, 1024-1029).
Log analysis: Review system logs (e.g., syslog) for errors related to RPC services, such as segmentation faults or core dumps, which could indicate a buffer overflow.
Intrusion Detection Systems (IDS): Implement and configure IDS rules to detect known exploit patterns associated with this vulnerability.
File Integrity Monitoring (FIM): Monitor critical system files for unauthorized modifications, which could be a sign of successful exploitation.
Host-based Intrusion Detection System (HIDS): Monitor for suspicious process execution or unusual system behavior.
Upgrade: Upgrade to a supported version of IBM AIX that addresses the vulnerability. This is the most effective solution.
Patching: Apply security patches provided by IBM for the affected AIX 4.3 systems, if available. Note that support for AIX 4.3 is likely discontinued.
Network Segmentation: Isolate vulnerable systems from the internet and untrusted networks to limit exposure.
Firewall Rules: Implement strict firewall rules to restrict access to RPC services, allowing only necessary traffic from trusted sources.
Intrusion Detection/Prevention Systems: Deploy and configure IDS/IPS to detect and block malicious RPC requests.
Least Privilege: Ensure that the RPC services run with the least privileges necessary to perform their functions.
Regular Security Audits: Conduct regular security audits and vulnerability scans to identify and address potential vulnerabilities.