CVE-2021-0248
📋 TL;DR
This vulnerability involves hard-coded credentials in Juniper Junos OS on NFX Series devices, allowing attackers to take over any NFX deployment instance through administrative interfaces. Only NFX Series devices running Junos OS versions prior to 19.1R1 are affected.
💻 Affected Systems
- Juniper Networks NFX Series devices
📦 What is this software?
Junos by Juniper
Junos OS is Juniper Networks' flagship network operating system running on enterprise routers, switches, security appliances, and data center infrastructure worldwide. Deployed across telecommunications providers, ISPs, cloud service providers, financial institutions, and large enterprises, Junos po...
Learn more about Junos →Junos by Juniper
Junos OS is Juniper Networks' flagship network operating system running on enterprise routers, switches, security appliances, and data center infrastructure worldwide. Deployed across telecommunications providers, ISPs, cloud service providers, financial institutions, and large enterprises, Junos po...
Learn more about Junos →⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of NFX Series device with full administrative control, potentially leading to network disruption, data exfiltration, or lateral movement.
Likely Case
Unauthorized administrative access to NFX devices, enabling configuration changes, service disruption, or credential harvesting.
If Mitigated
Limited impact if administrative interfaces are properly firewalled and access-controlled, though risk remains from insider threats or compromised management networks.
🎯 Exploit Status
Exploitation requires network access to administrative interfaces but uses hard-coded credentials, making it straightforward for attackers with such access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Junos OS 19.1R1 or later
Vendor Advisory: https://kb.juniper.net/JSA11141
Restart Required: Yes
Instructions:
1. Upgrade NFX Series devices to Junos OS 19.1R1 or later. 2. Follow Juniper's upgrade procedures for NFX devices. 3. Verify the upgrade completed successfully.
🔧 Temporary Workarounds
Restrict Administrative Interface Access
allLimit network access to NFX administrative interfaces using firewalls or access control lists to prevent unauthorized connections.
Network Segmentation
allIsolate NFX Series devices on separate management VLANs with strict access controls.
🧯 If You Can't Patch
- Implement strict network segmentation to isolate NFX devices from untrusted networks.
- Monitor administrative interface access logs for unauthorized login attempts using hard-coded credentials.
🔍 How to Verify
Check if Vulnerable:
Check Junos OS version on NFX Series devices: 'show version' and verify if version is prior to 19.1R1.Check Version:
show versionVerify Fix Applied:
After upgrade, run 'show version' to confirm Junos OS version is 19.1R1 or later.📡 Detection & Monitoring
Log Indicators:
- Failed or successful authentication attempts using hard-coded credentials in system logs
- Unauthorized configuration changes on NFX devices
Network Indicators:
- Unexpected administrative connections to NFX devices
- Traffic patterns indicating device compromise
SIEM Query:
Search for authentication events from NFX devices with suspicious source IPs or credential patterns matching known hard-coded credentials.