CVE-2021-23855
📋 TL;DR
CVE-2021-23855 exposes user credentials through an unprotected web server resource in affected Bosch products. Attackers can retrieve weakly hashed passwords and crack them using rainbow tables. This affects Bosch Rexroth ctrlX CORE and ctrlX COREremote devices.
💻 Affected Systems
- Bosch Rexroth ctrlX CORE
- Bosch Rexroth ctrlX COREremote
📦 What is this software?
Rexroth Indramotion Mlc Firmware by Bosch
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with administrative access, credential theft enabling lateral movement, and potential ransomware deployment.
Likely Case
Unauthorized access to the device, credential harvesting for password reuse attacks, and data exfiltration.
If Mitigated
Limited impact with proper network segmentation and strong authentication controls in place.
🎯 Exploit Status
Simple HTTP request to unprotected endpoint retrieves password database. Weak hashing (MD5) enables trivial password cracking.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: V1.5 or later
Vendor Advisory: https://psirt.bosch.com/security-advisories/bosch-sa-741752.html
Restart Required: Yes
Instructions:
1. Download firmware V1.5 or later from Bosch Rexroth support portal. 2. Backup device configuration. 3. Apply firmware update via web interface or USB. 4. Verify successful update and restore configuration.
🔧 Temporary Workarounds
Network Isolation
linuxRestrict network access to affected devices using firewall rules.
iptables -A INPUT -p tcp --dport 443 -s trusted_ip -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP
Disable Web Interface
linuxTurn off web server if not required for operations.
systemctl stop ctrlx-web-server
systemctl disable ctrlx-web-server
🧯 If You Can't Patch
- Implement strict network segmentation to isolate affected devices from untrusted networks.
- Enforce strong password policies and monitor for credential reuse across systems.
🔍 How to Verify
Check if Vulnerable:
Access https://device-ip/path/to/userdb endpoint. If it returns user/password data, device is vulnerable.Check Version:
ssh admin@device-ip 'cat /etc/ctrlx-version'Verify Fix Applied:
Attempt to access the user database endpoint after patching - should return 404 or access denied.📡 Detection & Monitoring
Log Indicators:
- HTTP 200 responses to user database endpoint
- Multiple failed login attempts from new IPs
Network Indicators:
- HTTP GET requests to /path/to/userdb from unauthorized sources
- Unusual outbound traffic post-authentication
SIEM Query:
source="web_logs" AND (uri="/path/to/userdb" OR status=200 AND uri LIKE "%userdb%")