CVE-2020-27866
📋 TL;DR
This vulnerability allows network-adjacent attackers to bypass authentication on affected NETGEAR routers by exploiting incorrect string matching logic in the mini_httpd service. Attackers can leverage this with other vulnerabilities to execute code as root. Affected users include anyone using the listed NETGEAR router models.
💻 Affected Systems
- NETGEAR R6020
- R6080
- R6120
- R6220
- R6260
- R6700v2
- R6800
- R6900v2
- R7450
- JNR3210
- WNR2020
- Nighthawk AC2100
- Nighthawk AC2400
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Full router compromise with root code execution, allowing attackers to intercept traffic, modify configurations, install malware, or pivot to internal networks.
Likely Case
Authentication bypass leading to unauthorized access to router admin interface, configuration changes, and potential credential theft.
If Mitigated
Limited impact if routers are behind firewalls, have restricted network access, or use non-default configurations.
🎯 Exploit Status
Exploit requires network access to router's web interface. Combined with other vulnerabilities for full RCE. ZDI advisory ZDI-20-1451 provides technical details.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check NETGEAR security advisory for specific firmware versions per model
Vendor Advisory: https://kb.netgear.com/000062641/Security-Advisory-for-Password-Recovery-Vulnerabilities-on-Some-Routers
Restart Required: Yes
Instructions:
1. Visit NETGEAR support site. 2. Download latest firmware for your router model. 3. Log into router admin interface. 4. Navigate to Advanced > Administration > Firmware Update. 5. Upload and install new firmware. 6. Router will reboot automatically.
🔧 Temporary Workarounds
Disable remote management
allPrevents external access to router web interface
Change default admin password
allMitigates impact if authentication bypass occurs
🧯 If You Can't Patch
- Segment router management interface to restricted VLAN
- Implement network access controls to limit who can reach router web interface
🔍 How to Verify
Check if Vulnerable:
Check router firmware version against NETGEAR advisory. If version is older than patched version listed for your model, you are vulnerable.Check Version:
Log into router web interface and check firmware version under Advanced > Administration > Router StatusVerify Fix Applied:
Verify firmware version matches or exceeds patched version from NETGEAR advisory. Test authentication bypass is no longer possible.📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts followed by successful access
- Unusual admin interface access from unexpected IPs
- Configuration changes without authorized user activity
Network Indicators:
- HTTP requests to router IP on port 80 with unusual patterns
- Traffic spikes to router management interface
SIEM Query:
source_ip=router_ip AND dest_port=80 AND (http_method=POST OR http_uri CONTAINS 'password' OR 'admin')🔗 References
- https://kb.netgear.com/000062641/Security-Advisory-for-Password-Recovery-Vulnerabilities-on-Some-Routers
- https://www.zerodayinitiative.com/advisories/ZDI-20-1451/
- https://kb.netgear.com/000062641/Security-Advisory-for-Password-Recovery-Vulnerabilities-on-Some-Routers
- https://www.zerodayinitiative.com/advisories/ZDI-20-1451/
