CVE-2025-36251
📋 TL;DR
This vulnerability in IBM AIX and VIOS nimsh service allows remote attackers to execute arbitrary commands due to improper SSL/TLS process controls. It affects IBM AIX 7.2, 7.3 and IBM VIOS 3.1, 4.1 systems with the nimsh service enabled. This is an additional attack vector for a previously addressed vulnerability (CVE-2024-56347).
💻 Affected Systems
- IBM AIX
- IBM VIOS
📦 What is this software?
Aix by Ibm
Aix by Ibm
⚠️ Risk & Real-World Impact
Worst Case
Remote unauthenticated attacker gains full root-level command execution on affected systems, leading to complete system compromise, data theft, and lateral movement.
Likely Case
Remote attacker executes arbitrary commands with elevated privileges, potentially installing malware, exfiltrating data, or disrupting services.
If Mitigated
If proper network segmentation and access controls are in place, impact is limited to isolated segments with no critical data exposure.
🎯 Exploit Status
Based on CVSS 9.6 score and CWE-114 (Process Control), exploitation appears straightforward for attackers with network access to nimsh service.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Apply interim fix or service pack as specified in IBM advisory
Vendor Advisory: https://www.ibm.com/support/pages/node/7251173
Restart Required: Yes
Instructions:
1. Review IBM advisory at provided URL. 2. Download appropriate interim fix or service pack. 3. Apply patch following IBM installation procedures. 4. Restart affected services or system as required.
🔧 Temporary Workarounds
Disable nimsh service
allTemporarily disable the vulnerable nimsh service if not required
stopsrc -s nimsh
chssys -s nimsh -d
Network access restriction
allRestrict network access to nimsh service using firewall rules
iptables -A INPUT -p tcp --dport 3901 -j DROP
chsec -f /etc/security/firewall -s default -a "block in proto tcp from any to any port 3901"
🧯 If You Can't Patch
- Implement strict network segmentation to isolate affected systems
- Monitor nimsh service logs for unusual activity and implement intrusion detection
🔍 How to Verify
Check if Vulnerable:
Check if nimsh service is running: lssrc -s nimshCheck Version:
oslevel -sVerify Fix Applied:
Verify patch installation: instfix -i | grep IX\d+ for interim fixes or oslevel -s for service packs📡 Detection & Monitoring
Log Indicators:
- Unusual command execution via nimsh in /var/adm/ras/nimsh.log
- Failed authentication attempts to nimsh service
Network Indicators:
- Unexpected connections to TCP port 3901 (nimsh default)
- SSL/TLS handshake anomalies to nimsh service
SIEM Query:
source="nimsh.log" AND (command="*" OR auth_failure="*")