CVE-2021-3705
📋 TL;DR
CVE-2021-3705 is a critical vulnerability in certain HP LaserJet Pro printers that allows unauthorized attackers to reconfigure or factory reset devices without authentication. This affects HP LaserJet Pro printers with specific firmware versions. Attackers can exploit this vulnerability over the network to gain control of affected printers.
💻 Affected Systems
- HP LaserJet Pro printers
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of printer functionality, including device reconfiguration, data exposure from print jobs, and potential use as an internal network pivot point.
Likely Case
Unauthorized factory resets disrupting printer operations, configuration changes causing service interruptions, and potential exposure of sensitive printed documents.
If Mitigated
Limited impact with proper network segmentation and access controls preventing unauthorized network access to printer management interfaces.
🎯 Exploit Status
Exploitation requires network access to the printer but no authentication, making it relatively simple to execute.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firmware updates as specified in HP Security Bulletin HPSBPI03741
Vendor Advisory: https://support.hp.com/us-en/document/ish_4411563-4411589-16/hpsbpi03741
Restart Required: Yes
Instructions:
1. Visit HP support site and download latest firmware for your printer model. 2. Upload firmware to printer via web interface or network management tools. 3. Apply update and restart printer as prompted.
🔧 Temporary Workarounds
Network Segmentation
allIsolate printers on separate VLANs with strict firewall rules limiting access to management interfaces.
Disable Unnecessary Services
allDisable remote management features not required for operations.
🧯 If You Can't Patch
- Implement strict network access controls to limit printer management interface access to authorized administrators only.
- Monitor printer logs for unauthorized configuration changes or factory reset events.
🔍 How to Verify
Check if Vulnerable:
Check printer firmware version via web interface or management console and compare against HP's vulnerable versions list.Check Version:
Access printer web interface at http://[printer-ip] and navigate to Information or Settings page to view firmware version.Verify Fix Applied:
Verify firmware version has been updated to non-vulnerable version specified in HP advisory.📡 Detection & Monitoring
Log Indicators:
- Unexpected factory reset events
- Configuration changes from unauthorized IP addresses
- Failed authentication attempts on management interface
Network Indicators:
- Unusual HTTP/HTTPS traffic to printer management ports (typically 80, 443, 9100)
- Configuration requests from non-admin IP addresses
SIEM Query:
source="printer_logs" AND (event="factory_reset" OR event="config_change") AND user="unknown"