CVE-2021-20697
📋 TL;DR
CVE-2021-20697 is an authentication bypass vulnerability in D-Link DAP-1880AC access points. It allows remote attackers to gain administrative access without credentials via unspecified vectors. This affects firmware version 1.21 and earlier.
💻 Affected Systems
- D-Link DAP-1880AC
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing attacker to reconfigure network settings, intercept traffic, install backdoors, or use device as pivot point into internal network.
Likely Case
Unauthorized administrative access leading to network configuration changes, traffic monitoring, or device takeover for malicious purposes.
If Mitigated
Limited impact if device is behind firewall with strict inbound rules and network segmentation prevents lateral movement.
🎯 Exploit Status
Authentication bypass vulnerabilities are typically easy to exploit once the vector is identified.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firmware version 1.22 or later
Vendor Advisory: https://www.dlink-jp.com/support/release/jvnvu92898656_dap-1880ac.html
Restart Required: Yes
Instructions:
1. Download firmware version 1.22 or later from D-Link Japan support site. 2. Log into device web interface. 3. Navigate to System > Firmware Update. 4. Upload and apply new firmware. 5. Device will reboot automatically.
🔧 Temporary Workarounds
Network Isolation
allPlace device behind firewall with strict inbound rules and isolate from critical network segments.
Access Control Lists
allImplement network ACLs to restrict access to device management interface.
🧯 If You Can't Patch
- Replace device with non-vulnerable model or updated hardware
- Decommission device and remove from network entirely
🔍 How to Verify
Check if Vulnerable:
Check firmware version in web interface under System > Firmware Information. If version is 1.21 or earlier, device is vulnerable.Check Version:
No CLI command available. Must use web interface at http://[device-ip]/System/firmware.aspVerify Fix Applied:
After update, verify firmware version shows 1.22 or later in System > Firmware Information.📡 Detection & Monitoring
Log Indicators:
- Multiple failed login attempts followed by successful login from same IP
- Configuration changes from unexpected IP addresses
- Login events without corresponding authentication attempts
Network Indicators:
- HTTP requests to management interface from unauthorized IPs
- Unusual configuration changes via network traffic
SIEM Query:
source="dap-1880ac-logs" AND (event="login_success" NOT preceding(event="auth_attempt") WITHIN 5s)