CVE-2021-0276
📋 TL;DR
A stack-based buffer overflow vulnerability in Juniper Networks SBR Carrier with EAP authentication allows attackers to crash the RADIUS daemon, causing denial of service or potentially remote code execution. This affects Juniper SBR Carrier versions 8.4.1, 8.5.0, and 8.6.0 before specific patch releases. Organizations using these versions with EAP authentication configured are vulnerable.
💻 Affected Systems
- Juniper Networks SBR Carrier
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise and potential lateral movement within the network.
Likely Case
Sustained denial of service through repeated RADIUS daemon crashes, disrupting authentication services.
If Mitigated
Limited impact with proper network segmentation and intrusion prevention systems blocking malicious packets.
🎯 Exploit Status
Exploitation requires sending specific packets to the RADIUS service, which typically listens on UDP ports 1812/1813 or 1645/1646.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 8.4.1R19, 8.5.0R10, or 8.6.0R4
Vendor Advisory: https://kb.juniper.net/JSA11180
Restart Required: Yes
Instructions:
1. Download the appropriate patch version from Juniper support portal. 2. Backup current configuration. 3. Apply the patch following Juniper's upgrade procedures. 4. Restart the SBR Carrier system. 5. Verify the new version is running.
🔧 Temporary Workarounds
Disable EAP Authentication
allTemporarily disable EAP authentication on the RADIUS daemon if not required for operations.
# Configuration commands vary by setup. Consult Juniper documentation for specific EAP disable commands.
Network Access Control
allRestrict access to RADIUS ports (UDP 1812/1813, 1645/1646) to trusted sources only.
# Example firewall rule (syntax varies by firewall):
# deny udp any any eq 1812
# deny udp any any eq 1813
# permit udp trusted_networks any eq 1812
# permit udp trusted_networks any eq 1813
🧯 If You Can't Patch
- Implement strict network segmentation to isolate RADIUS services from untrusted networks.
- Deploy intrusion prevention systems (IPS) with signatures for buffer overflow attacks on RADIUS services.
🔍 How to Verify
Check if Vulnerable:
Check if running affected versions (8.4.1 < R19, 8.5.0 < R10, 8.6.0 < R4) with EAP authentication enabled. Use 'show version' command on SBR Carrier CLI.Check Version:
show versionVerify Fix Applied:
Verify the version is 8.4.1R19, 8.5.0R10, or 8.6.0R4 or later using 'show version' command.📡 Detection & Monitoring
Log Indicators:
- RADIUS daemon crash logs
- Unexpected process termination of radiusd
- Authentication failures during attack
Network Indicators:
- Unusual volume of RADIUS packets from single sources
- Malformed RADIUS packets to UDP ports 1812/1813
SIEM Query:
source="radiusd" AND (event="crash" OR event="terminated") OR (destination_port IN (1812, 1813, 1645, 1646) AND packet_size > normal_threshold)