CVE-2024-39562
📋 TL;DR
A resource management vulnerability in xinetd on Juniper Junos OS Evolved allows unauthenticated attackers to cause denial of service by sending high rates of SSH connections. When exploited, xinetd crashes leaving defunct sshd processes that block SSH, SFTP, and Netconf over SSH access. This affects Junos OS Evolved versions 21.4 through 23.2 with specific vulnerable releases.
💻 Affected Systems
- Juniper Networks Junos OS Evolved
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete loss of SSH-based management access requiring manual intervention to restore service, potentially disrupting network operations and remote administration.
Likely Case
Temporary denial of SSH services during attack periods, requiring administrator monitoring and potential service restarts.
If Mitigated
Limited impact with proper network controls and monitoring, allowing quick detection and response before service disruption.
🎯 Exploit Status
Exploitation requires sending high rate of SSH connections with specific termination patterns. No authentication required.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 21.4R3-S7-EVO, 22.3R2-S2-EVO, 22.3R3-S2-EVO, 22.4R3-EVO, or 23.2R2-EVO
Vendor Advisory: https://supportportal.juniper.net/JSA75724
Restart Required: Yes
Instructions:
1. Download appropriate patched version from Juniper support portal. 2. Install update following Junos OS Evolved upgrade procedures. 3. Reboot device to complete installation.
🔧 Temporary Workarounds
Monitor and Clean Defunct Processes
linuxRegularly check for defunct sshd processes and restart xinetd service if detected
show system processes | match sshd
restart xinetd
🧯 If You Can't Patch
- Implement network access controls to limit SSH connections to trusted sources only
- Deploy rate limiting on SSH connections using network security devices
🔍 How to Verify
Check if Vulnerable:
Check current version with 'show version' and compare against affected versions listCheck Version:
show versionVerify Fix Applied:
Verify version is patched with 'show version' and check for defunct sshd processes with 'show system processes | match sshd'📡 Detection & Monitoring
Log Indicators:
- xinetd crash logs
- unusual SSH connection patterns
- high rate of SSH connection attempts
Network Indicators:
- Spike in SSH connection attempts from single/multiple sources
- SSH service unresponsive after connection bursts
SIEM Query:
source="junos" AND (process="xinetd" AND status="crashed") OR (process="sshd" AND state="defunct")