CVE-2021-33516
📋 TL;DR
This CVE describes a DNS rebinding vulnerability in GUPnP libraries that allows remote attackers to bypass same-origin policy protections. Attackers can trick victims' browsers into making requests to local UPnP services, potentially leading to unauthorized actions. Systems using vulnerable GUPnP versions for UPnP service implementations are affected.
💻 Affected Systems
- GUPnP library
- Applications using GUPnP for UPnP services
📦 What is this software?
Gupnp by Gnome
Gupnp by Gnome
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of local UPnP services allowing data exfiltration, service manipulation, or execution of unauthorized commands on affected devices.
Likely Case
Unauthorized access to UPnP services leading to data exposure or service disruption.
If Mitigated
Limited impact with proper network segmentation and browser security controls.
🎯 Exploit Status
Requires DNS rebinding attack against victim's browser and vulnerable local UPnP service.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: GUPnP 1.0.7, 1.2.5, or later
Vendor Advisory: https://discourse.gnome.org/t/security-relevant-releases-for-gupnp-issue-cve-2021-33516/6536
Restart Required: Yes
Instructions:
1. Update GUPnP to version 1.0.7 or 1.2.5 or later. 2. Restart affected services using GUPnP. 3. Verify the update was successful.
🔧 Temporary Workarounds
Network Segmentation
allIsolate UPnP services from untrusted networks
Browser DNS Rebinding Protection
allEnable DNS rebinding protection in browsers
🧯 If You Can't Patch
- Implement strict network segmentation to isolate UPnP services
- Deploy web application firewalls to detect DNS rebinding attempts
🔍 How to Verify
Check if Vulnerable:
Check GUPnP library version using package manager: dpkg -l | grep gupnp or rpm -qa | grep gupnpCheck Version:
pkg-config --modversion gupnp-1.0Verify Fix Applied:
Verify installed GUPnP version is 1.0.7 or 1.2.5 or later📡 Detection & Monitoring
Log Indicators:
- Unusual DNS queries from browsers
- Unexpected UPnP service requests from browser user-agents
Network Indicators:
- DNS rebinding patterns
- Cross-origin requests to local UPnP services
SIEM Query:
source="browser_logs" AND (dns_query="*.attacker.com" OR destination_ip="192.168.*")