CVE-2024-20397
📋 TL;DR
This vulnerability allows attackers to bypass Cisco NX-OS image signature verification, enabling them to load unverified or malicious software onto affected devices. It affects Cisco Nexus switches and MDS switches running vulnerable NX-OS versions. Attackers need either physical access to the device or administrative credentials to exploit this.
💻 Affected Systems
- Cisco Nexus 3000 Series Switches
- Cisco Nexus 9000 Series Switches in standalone NX-OS mode
- Cisco MDS 9000 Series Multilayer Switches
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
An attacker could load persistent malware or backdoored firmware, gaining complete control over network infrastructure, intercepting traffic, or disrupting operations.
Likely Case
Malicious insiders or attackers with physical access could install unauthorized software to maintain persistence or bypass security controls.
If Mitigated
With proper physical security and administrative access controls, exploitation risk is significantly reduced.
🎯 Exploit Status
Exploitation requires executing specific bootloader commands, which needs either physical console access or administrative SSH/Telnet access to the device.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: NX-OS 10.4(3) and later
Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-image-sig-bypas-pQDRQvjL
Restart Required: Yes
Instructions:
1. Download the patched NX-OS version from Cisco Software Center. 2. Upload the image to the switch. 3. Install the new image using 'install all' command. 4. Reboot the device to complete the upgrade.
🔧 Temporary Workarounds
Restrict Physical Access
allImplement strict physical security controls to prevent unauthorized access to console ports.
Secure Administrative Access
allImplement strong authentication, authorization, and accounting (AAA) for administrative access, and limit administrative privileges.
🧯 If You Can't Patch
- Implement strict physical security controls including locked racks, surveillance, and access logs for data center equipment.
- Enforce least privilege for administrative accounts, implement multi-factor authentication, and monitor for unusual administrative activity.
🔍 How to Verify
Check if Vulnerable:
Check NX-OS version with 'show version' command. If version is earlier than 10.4(3), the device is vulnerable.Check Version:
show version | include "NX-OS"Verify Fix Applied:
After upgrade, run 'show version' to confirm version is 10.4(3) or later.📡 Detection & Monitoring
Log Indicators:
- Bootloader command execution logs
- Unauthorized image installation attempts
- Unexpected system reboots
Network Indicators:
- Unusual administrative SSH/Telnet connections to affected devices
SIEM Query:
Search for events containing 'bootloader', 'image verification failed', or 'unauthorized software load' on Cisco NX-OS devices.