CVE-2018-0308
📋 TL;DR
A buffer overflow vulnerability in Cisco Fabric Services allows unauthenticated remote attackers to execute arbitrary code or cause denial of service on affected Cisco networking devices. The vulnerability exists due to insufficient validation of packet headers in Cisco Fabric Services. This affects numerous Cisco switches, firewalls, and fabric interconnects when configured to use Cisco Fabric Services.
💻 Affected Systems
- Firepower 4100 Series Next-Generation Firewalls
- Firepower 9300 Security Appliance
- MDS 9000 Series Multilayer Switches
- Nexus 2000 Series Fabric Extenders
- Nexus 3000 Series Switches
- Nexus 3500 Platform Switches
- Nexus 5500 Platform Switches
- Nexus 5600 Platform Switches
- Nexus 6000 Series Switches
- Nexus 7000 Series Switches
- Nexus 7700 Series Switches
- Nexus 9000 Series Switches in standalone NX-OS mode
- Nexus 9500 R-Series Line Cards and Fabric Modules
- UCS 6100 Series Fabric Interconnects
- UCS 6200 Series Fabric Interconnects
- UCS 6300 Series Fabric Interconnects
📦 What is this software?
Unified Computing System Firmware by Cisco
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, lateral movement within network, and persistent backdoor installation.
Likely Case
Denial of service causing device crashes and network disruption, potentially requiring physical intervention to restore service.
If Mitigated
Limited impact if proper network segmentation and access controls prevent unauthorized access to Cisco Fabric Services ports.
🎯 Exploit Status
The vulnerability requires sending crafted Cisco Fabric Services packets to TCP port 32015 or UDP port 32015. No authentication is required, making exploitation straightforward for attackers with network access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Varies by product - see Cisco Security Advisory for specific fixed versions
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180620-fxnxos-fab-ace
Restart Required: Yes
Instructions:
1. Identify affected devices using 'show version' command. 2. Download appropriate fixed software from Cisco Software Center. 3. Follow Cisco's upgrade procedures for your specific device model. 4. Reboot device after upgrade to load patched software.
🔧 Temporary Workarounds
Disable Cisco Fabric Services
allIf Cisco Fabric Services is not required, disable it to eliminate the attack vector
feature-set fabric
no feature-set fabric
Restrict Access to Cisco Fabric Services Ports
allImplement access control lists to restrict access to TCP/UDP port 32015
access-list 100 deny ip any any eq 32015
access-list 100 permit ip any any
🧯 If You Can't Patch
- Implement strict network segmentation to isolate affected devices from untrusted networks
- Deploy intrusion prevention systems with signatures for CVE-2018-0308 exploitation attempts
🔍 How to Verify
Check if Vulnerable:
Check if device is in affected product list and running unpatched software using 'show version' commandCheck Version:
show version | include SoftwareVerify Fix Applied:
Verify software version is at or above the fixed version listed in Cisco Security Advisory📡 Detection & Monitoring
Log Indicators:
- Unexpected device reboots
- Cisco Fabric Services process crashes
- Memory corruption errors in system logs
Network Indicators:
- Unusual traffic to TCP/UDP port 32015
- Crafted packets with malformed Cisco Fabric Services headers
SIEM Query:
source_port:32015 OR dest_port:32015 AND (protocol:TCP OR protocol:UDP) AND (payload_contains:"malformed" OR size_anomaly:true)🔗 References
- http://www.securityfocus.com/bid/104514
- http://www.securitytracker.com/id/1041169
- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180620-fxnxos-fab-ace
- http://www.securityfocus.com/bid/104514
- http://www.securitytracker.com/id/1041169
- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180620-fxnxos-fab-ace
