CVE-2023-31926
📋 TL;DR
This vulnerability in Brocade Fabric OS allows local users to overwrite system files using the 'less' command. It affects Brocade SAN switches running vulnerable Fabric OS versions. Attackers could modify critical system files to gain elevated privileges or disrupt operations.
💻 Affected Systems
- Brocade SAN Switches with Fabric OS
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing privilege escalation to root, persistent backdoor installation, or denial of service by corrupting critical system files.
Likely Case
Local privilege escalation allowing authenticated users to gain administrative access to the switch, potentially leading to configuration changes or data access.
If Mitigated
Limited impact if proper access controls restrict local user access and file permissions are properly configured.
🎯 Exploit Status
Exploitation requires local CLI access. The vulnerability is in the 'less' command's file handling capabilities.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Brocade Fabric OS v9.1.1c or v9.2.0 and later
Vendor Advisory: https://support.broadcom.com/external/content/SecurityAdvisories/0/22388
Restart Required: Yes
Instructions:
1. Download the appropriate Fabric OS update from Broadcom support portal. 2. Upload the firmware to the switch. 3. Install the update using the 'firmwareDownload' command. 4. Reboot the switch to complete installation.
🔧 Temporary Workarounds
Restrict CLI Access
allLimit local CLI access to trusted administrators only using RBAC and access controls.
userconfig --add <username> <role>
userconfig --modify <username> <newrole>
Monitor File Changes
allImplement file integrity monitoring for critical system files to detect unauthorized modifications.
🧯 If You Can't Patch
- Implement strict role-based access control (RBAC) to limit who has CLI access to switches
- Monitor and audit all CLI sessions and file modification activities on affected switches
🔍 How to Verify
Check if Vulnerable:
Check Fabric OS version: 'version' command. If version is below v9.1.1c or v9.2.0, system is vulnerable.Check Version:
versionVerify Fix Applied:
After patching, run 'version' command to confirm Fabric OS is v9.1.1c, v9.2.0, or later.📡 Detection & Monitoring
Log Indicators:
- Unexpected file modification events in system logs
- Unauthorized privilege escalation attempts
- Abnormal 'less' command usage with file write operations
Network Indicators:
- Unusual CLI session patterns or access from unexpected sources
SIEM Query:
source="brocade_switch" AND (event_type="file_modification" OR command="less" AND parameters LIKE "%>%")