CVE-2021-20695
📋 TL;DR
This vulnerability in D-Link DAP-1880AC firmware allows remote authenticated attackers to bypass certificate chain of trust validation, potentially gaining root privileges. It affects firmware version 1.21 and earlier. Attackers must have authenticated access to exploit this flaw.
💻 Affected Systems
- D-Link DAP-1880AC Wireless AC1200 Dual Band Gigabit Range Extender
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote authenticated attacker gains full root access to the device, enabling complete compromise, data theft, network pivoting, and persistent backdoor installation.
Likely Case
Authenticated attacker escalates privileges to root, allowing configuration changes, credential harvesting, and network reconnaissance.
If Mitigated
With proper network segmentation and access controls, impact is limited to the affected device only.
🎯 Exploit Status
Exploitation requires authenticated access; specific vectors are unspecified in public disclosures.
🛠️ 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 the new firmware. 5. Device will reboot automatically.
🔧 Temporary Workarounds
Restrict administrative access
allLimit administrative interface access to trusted IP addresses only.
Configure firewall rules to restrict access to device management interface (typically port 80/443)
Change default credentials
allUse strong, unique administrative passwords to reduce risk of authenticated access.
Log into web interface > System > Admin > Change password
🧯 If You Can't Patch
- Isolate device on separate VLAN with strict network segmentation
- Disable remote management and only allow local console access if possible
🔍 How to Verify
Check if Vulnerable:
Check firmware version in web interface: System > Firmware > Current Version. If version is 1.21 or earlier, device is vulnerable.Check Version:
curl -k https://[device-ip]/getcfg.php | grep -i firmwareVerify Fix Applied:
After update, verify firmware version shows 1.22 or later in System > Firmware > Current Version.📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts followed by successful login
- Unusual configuration changes or firmware update attempts
- Root privilege escalation in system logs
Network Indicators:
- Unusual outbound connections from device after administrative login
- Traffic to unexpected ports or IP addresses
SIEM Query:
source="dap-1880ac" AND (event_type="authentication" AND result="success") FOLLOWED BY event_type="privilege_escalation" WITHIN 5m