CVE-2020-9279
📋 TL;DR
CVE-2020-9279 is a critical vulnerability in D-Link DSL-2640B routers where a hard-coded privileged account allows attackers to log into the management interface with administrative privileges. This affects all users of D-Link DSL-2640B B2 EU_4.01B devices, enabling complete device takeover. Attackers can perform critical tasks like changing configurations, intercepting traffic, or deploying malware.
💻 Affected Systems
- D-Link DSL-2640B
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing attackers to intercept all network traffic, deploy persistent malware, pivot to internal networks, and use the device as part of a botnet.
Likely Case
Unauthorized administrative access leading to network configuration changes, DNS hijacking, credential theft, and potential lateral movement to connected devices.
If Mitigated
Limited impact if device is behind firewall with restricted management interface access, though risk remains if internal attackers exist.
🎯 Exploit Status
Exploitation requires only knowledge of the hard-coded credentials and access to the management interface. Public advisories detail the specific account credentials.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check D-Link security bulletin for updated firmware
Vendor Advisory: https://www.dlink.com/en/security-bulletin
Restart Required: Yes
Instructions:
1. Visit D-Link support website 2. Download latest firmware for DSL-2640B 3. Log into router admin interface 4. Navigate to firmware update section 5. Upload and apply new firmware 6. Reboot router
🔧 Temporary Workarounds
Restrict Management Interface Access
allLimit access to router management interface to trusted IP addresses only
Configure firewall rules to block external access to ports 80/443 (HTTP/HTTPS) and 23 (Telnet) from untrusted networks
Disable Remote Management
allTurn off remote administration features
In router admin: Advanced > Remote Management > Disable
🧯 If You Can't Patch
- Replace affected devices with supported models that receive security updates
- Segment network to isolate router from critical systems and implement strict firewall rules
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin interface under Maintenance > Device Info. If version is B2 EU_4.01B, device is vulnerable.Check Version:
Connect to router and check web interface or use: telnet [router_ip] (if enabled) and check version infoVerify Fix Applied:
After firmware update, verify version has changed from B2 EU_4.01B. Attempt to login with known hard-coded credentials should fail.📡 Detection & Monitoring
Log Indicators:
- Failed login attempts followed by successful login with unusual username
- Administrative configuration changes from unexpected IP addresses
- Multiple login attempts from external IPs
Network Indicators:
- Unexpected administrative traffic from external sources
- Port scanning targeting router management ports (80, 443, 23)
- Unusual outbound connections from router
SIEM Query:
source="router_logs" AND (event_type="login_success" AND username="[hardcoded_account]") OR (event_type="config_change" AND source_ip NOT IN trusted_ips)🔗 References
- https://raelize.com/advisories/CVE-2020-9279_D-Link-DSL-2640B_Hard-coded-privileged-account_v1.0.txt
- https://raelize.com/posts/d-link-dsl-2640b-security-advisories/
- https://www.dlink.com/en/security-bulletin
- https://raelize.com/advisories/CVE-2020-9279_D-Link-DSL-2640B_Hard-coded-privileged-account_v1.0.txt
- https://raelize.com/posts/d-link-dsl-2640b-security-advisories/
- https://www.dlink.com/en/security-bulletin
