CVE-2024-56347: IBM AIX nimsh Service RCE Vulnerability

CVE-2024-56347 Overview

IBM AIX versions 7.2 and 7.3 contain a critical vulnerability in the nimsh service's SSL/TLS protection mechanisms. This flaw allows remote attackers to execute arbitrary commands on affected systems due to improper process controls. The nimsh service, which provides Network Installation Management (NIM) functionality over secure connections, fails to properly validate and control process execution, creating a dangerous attack surface for network-accessible systems.

Critical Impact

Remote attackers can execute arbitrary commands on vulnerable IBM AIX systems through the nimsh service, potentially leading to complete system compromise without requiring authentication.

Affected Products

• IBM AIX 7.2
• IBM AIX 7.3
• IBM AIX (all versions utilizing the vulnerable nimsh service)

Discovery Timeline

• 2025-03-18 - CVE CVE-2024-56347 published to NVD
• 2025-07-25 - Last updated in NVD database

Technical Details for CVE-2024-56347

Vulnerability Analysis

This vulnerability (CWE-114: Process Control) affects the nimsh service in IBM AIX, which is the secure shell component of the Network Installation Management subsystem. The nimsh service is designed to provide encrypted communication channels for NIM operations, but a flaw in its process control implementation allows attackers to inject and execute arbitrary commands.

The vulnerability requires user interaction for successful exploitation, where an attacker could craft malicious requests that bypass the SSL/TLS protection mechanisms. Once exploited, the scope of the attack extends beyond the vulnerable component, potentially affecting other resources on the same system or network segment. The impact includes complete compromise of confidentiality, integrity, and availability of the affected system.

Root Cause

The root cause of this vulnerability lies in improper process controls within the nimsh service's SSL/TLS implementation. The service fails to adequately validate and sanitize process-related operations, allowing attackers to manipulate how commands are executed within the service context. This CWE-114 (Process Control) weakness occurs when external input influences or controls the execution of a process, enabling attackers to redirect execution flow or inject malicious commands.

Attack Vector

The attack is network-based, meaning adversaries can target vulnerable systems remotely without requiring local access. The attack complexity is low, indicating that exploitation does not require specialized conditions or extensive preparation. While no authentication is required, some form of user interaction is necessary for successful exploitation—such as an administrator interacting with a malicious NIM request or service.

Attackers targeting this vulnerability would typically:

1. Identify IBM AIX systems with the nimsh service exposed to the network
2. Craft malicious requests designed to exploit the process control weakness
3. Leverage the SSL/TLS protection mechanism flaws to inject commands
4. Execute arbitrary commands with the privileges of the nimsh service process

The changed scope means that successful exploitation can affect resources beyond the security scope of the vulnerable component, potentially allowing lateral movement or access to sensitive data across the system.

Detection Methods for CVE-2024-56347

Indicators of Compromise

• Unusual process spawning or command execution originating from the nimsh service
• Unexpected network connections to or from the nimsh service on port 3901 (default NIM secure port)
• Anomalous entries in /var/adm/ras/nimlog or system audit logs related to NIM operations
• Unauthorized modifications to system files or configurations following nimsh service activity

Detection Strategies

• Monitor system calls and process creation events associated with the nimsh daemon for unauthorized command execution patterns
• Implement network traffic analysis to detect malformed or suspicious SSL/TLS handshakes targeting NIM services
• Deploy file integrity monitoring on critical system binaries and configurations that could be modified post-exploitation
• Audit nimsh service logs for authentication anomalies or unexpected administrative operations

Monitoring Recommendations

• Enable detailed auditing for all NIM-related services using the AIX Audit subsystem (audit start)
• Configure SIEM rules to alert on unusual command patterns executed by the nimsh service account
• Monitor for connections to the nimsh service from unexpected source IP addresses or network segments
• Establish baseline behavior for nimsh service operations and alert on deviations

How to Mitigate CVE-2024-56347

Immediate Actions Required

• Review and apply the security patches provided by IBM as documented in the official security bulletin
• Restrict network access to the nimsh service using firewall rules, limiting connections to trusted NIM master servers only
• Disable the nimsh service on systems where NIM over SSL/TLS is not required (stopsrc -s nimsh)
• Implement network segmentation to isolate systems running vulnerable nimsh services from untrusted networks

Patch Information

IBM has released security updates to address this vulnerability. System administrators should consult the IBM Support Page for this vulnerability for detailed patching instructions and download links. The security bulletin contains specific interim fixes (ifix) or service packs applicable to IBM AIX 7.2 and 7.3 environments.

Apply patches following IBM's recommended procedures:

1. Download the appropriate fix from IBM Fix Central
2. Review the fix README for installation prerequisites
3. Schedule a maintenance window as service restart may be required
4. Apply the fix using emgr or installp as directed
5. Verify successful installation and service functionality

Workarounds

• Disable SSL/TLS on the nimsh service if encrypted NIM communication is not required (nimconfig -c with appropriate settings)
• Use firewall rules via iptables or AIX packet filtering to restrict nimsh access to authorized NIM clients only
• Consider using alternative NIM communication methods (standard NIM without SSL) while awaiting patch deployment
• Implement jump hosts or bastion servers for any necessary remote NIM administration

# Configuration example - Restrict nimsh service access and disable if not needed

# Stop the nimsh service
stopsrc -s nimsh

# Disable automatic start of nimsh service
chssys -s nimsh -a "-a" 

# Alternatively, use firewall rules to restrict access (example using iptables)
# Allow nimsh (port 3901) only from trusted NIM master
/usr/sbin/iptables -A INPUT -p tcp --dport 3901 -s <trusted_nim_master_ip> -j ACCEPT
/usr/sbin/iptables -A INPUT -p tcp --dport 3901 -j DROP