CVE-2022-22351: IBM VIOS nimsh Daemon DoS Vulnerability

CVE-2022-22351 Overview

CVE-2022-22351 is a denial of service vulnerability affecting IBM AIX and VIOS systems. The vulnerability exists in the nimsh daemon, a component of the Network Installation Management (NIM) Service Handler. A non-privileged trusted host user can exploit this vulnerability to cause a denial of service condition in the nimsh daemon on another trusted host within the NIM environment.

Critical Impact

This network-accessible vulnerability allows attackers to disrupt nimsh daemon services across trusted hosts without requiring authentication, potentially impacting critical system management and deployment operations in enterprise AIX environments.

Affected Products

• IBM AIX 7.1 (all versions)
• IBM AIX 7.2 (including versions 7.2.5.0, 7.2.5.1, 7.2.5.100)
• IBM AIX 7.3 (including versions 7.3.0, 7.3.0 SP1)
• IBM VIOS 3.1 (all versions)

Discovery Timeline

• March 7, 2022 - CVE-2022-22351 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2022-22351

Vulnerability Analysis

This denial of service vulnerability affects the nimsh daemon, which is responsible for handling Network Installation Management (NIM) service communications in IBM AIX and VIOS environments. The nimsh daemon facilitates remote management operations between NIM masters and client systems within a trusted host configuration.

The vulnerability can be exploited by a non-privileged user on a trusted host to disrupt the nimsh daemon on another trusted host in the same NIM environment. This cross-host impact is particularly concerning as it allows lateral disruption across the NIM infrastructure without requiring elevated privileges on the attacking system.

The attack can be executed remotely over the network, requires low complexity to exploit, and does not require user interaction or authentication. While the vulnerability does not impact confidentiality or integrity, the availability impact is significant, potentially disrupting critical system management operations.

Root Cause

The vulnerability stems from improper handling of requests within the nimsh daemon when processing communications from trusted hosts. While IBM has not disclosed specific technical details regarding the exact flaw, the vulnerability is tracked under IBM X-Force ID: 220396. The weakness allows a non-privileged user to craft requests that cause the daemon to enter a denial of service state.

Attack Vector

The attack vector for CVE-2022-22351 is network-based, targeting the nimsh daemon which listens for NIM service requests. The vulnerability can be exploited in environments where NIM trusted host relationships are configured:

1. The attacker must have access as a non-privileged user on a system configured as a trusted host in the NIM environment
2. The attacker crafts malicious requests targeting the nimsh daemon on another trusted host
3. Upon processing the malicious request, the nimsh daemon on the target system enters a denial of service condition
4. NIM management operations on the affected host become unavailable until the service is restored

The exploitation does not require any authentication beyond the existing trusted host relationship, and no user interaction is needed on the target system.

Detection Methods for CVE-2022-22351

Indicators of Compromise

• Unexpected nimsh daemon crashes or service interruptions on AIX/VIOS systems
• Unusual network traffic patterns to the nimsh service port (typically port 3901)
• Repeated service restarts of the nimsh daemon in system logs
• NIM operations failing across trusted hosts without apparent cause

Detection Strategies

• Monitor nimsh daemon status and implement alerting for unexpected service terminations using lssrc -s nimsh
• Analyze system error reports (errpt) for nimsh-related failures and crashes
• Implement network monitoring to detect anomalous traffic patterns targeting NIM services
• Review audit logs for unusual activity from non-privileged users on trusted hosts

Monitoring Recommendations

• Configure system monitoring to track nimsh daemon availability and response times
• Implement centralized logging for all NIM-related events across the environment
• Set up alerts for multiple failed NIM operations that could indicate exploitation attempts
• Monitor network connections to nimsh services for unexpected source systems

How to Mitigate CVE-2022-22351

Immediate Actions Required

• Apply the security patches provided by IBM as documented in the IBM Support Advisory
• Review and restrict the list of NIM trusted hosts to only essential systems
• Implement network segmentation to limit access to nimsh services
• Monitor nimsh daemon operations for signs of exploitation

Patch Information

IBM has released security updates to address this vulnerability. Administrators should consult the IBM Support Advisory for specific patch information and installation instructions for their AIX or VIOS version. The IBM X-Force Vulnerability Report provides additional technical details about this vulnerability.

Patches should be applied to all affected systems running:

• IBM AIX 7.1, 7.2, 7.3
• IBM VIOS 3.1

Workarounds

• Restrict network access to the nimsh daemon using firewall rules to limit connections to authorized management systems only
• Disable the nimsh service on systems where NIM functionality is not required using stopsrc -s nimsh
• Implement strict access controls on trusted hosts to minimize the number of users who could potentially exploit this vulnerability
• Consider using alternative management methods for non-critical systems until patches can be applied

# Check nimsh daemon status
lssrc -s nimsh

# Stop nimsh service if not required
stopsrc -s nimsh

# View NIM trusted hosts configuration
lsnim -c machines

# Review error reports for nimsh issues
errpt -a | grep -i nim