CVE-2021-34202
📋 TL;DR
This vulnerability in D-Link DIR-2640 routers allows local attackers with ordinary user permissions to exploit out-of-bounds memory vulnerabilities to gain administrator privileges and execute arbitrary code. Attackers can combine this with other vulnerabilities to achieve remote code execution. Only D-Link DIR-2640 AC2600 routers running firmware version 1.01B04 are affected.
💻 Affected Systems
- D-Link DIR-2640 AC2600
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing attackers to install persistent malware, intercept all network traffic, pivot to internal networks, and use the device for botnet activities.
Likely Case
Local privilege escalation leading to unauthorized administrative access, configuration changes, and potential lateral movement within the network.
If Mitigated
Limited to local network access only if proper network segmentation and firewall rules prevent external access to router management interfaces.
🎯 Exploit Status
Requires local access initially but can be combined with other vulnerabilities for remote exploitation. Proof of concept code is publicly available on GitHub.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check D-Link security bulletin for latest patched version
Vendor Advisory: https://www.dlink.com/en/security-bulletin/
Restart Required: Yes
Instructions:
1. Visit D-Link support website 2. Download latest firmware for DIR-2640 3. Log into router admin interface 4. Navigate to firmware update section 5. Upload and apply new firmware 6. Reboot router
🔧 Temporary Workarounds
Disable remote management
allPrevent external access to router management interface
Login to router admin > Advanced > Remote Management > Disable
Network segmentation
allIsolate router management interface to separate VLAN
🧯 If You Can't Patch
- Replace affected router with updated model or different vendor
- Implement strict network access controls to limit who can access router management interface
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin interface under Status > FirmwareCheck Version:
Check via router web interface or SSH if enabled: cat /proc/version or show versionVerify Fix Applied:
Verify firmware version has been updated to a version later than 1.01B04📡 Detection & Monitoring
Log Indicators:
- Unusual privilege escalation attempts
- Multiple failed login attempts followed by successful admin login
- Unexpected firmware modification logs
Network Indicators:
- Unusual outbound connections from router
- Traffic patterns suggesting router compromise
- Unexpected management interface access from unauthorized IPs
SIEM Query:
source="router_logs" AND (event_type="privilege_escalation" OR (failed_login>=3 AND success_login="admin"))🔗 References
- http://d-link.com
- http://dir-2640-us.com
- https://github.com/liyansong2018/CVE/tree/main/2021/CVE-2021-34202
- https://www.dlink.com/en/security-bulletin/
- http://d-link.com
- http://dir-2640-us.com
- https://github.com/liyansong2018/CVE/tree/main/2021/CVE-2021-34202
- https://www.dlink.com/en/security-bulletin/
