CVE-2025-29516
📋 TL;DR
This CVE describes a command injection vulnerability in D-Link DSL-7740C routers that allows attackers to execute arbitrary commands via the backup function. Attackers can potentially gain full control of affected devices. This affects users of D-Link DSL-7740C routers with vulnerable firmware versions.
💻 Affected Systems
- D-Link DSL-7740C
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing attacker to install persistent backdoors, intercept network traffic, pivot to internal networks, and use device as botnet node.
Likely Case
Attacker gains shell access to router, modifies configuration, steals credentials, and disrupts network connectivity.
If Mitigated
Limited impact with proper network segmentation, firewall rules blocking router management interfaces, and regular monitoring.
🎯 Exploit Status
Proof of concept available in GitHub gist. Exploitation requires access to backup function which typically requires authentication.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check D-Link security bulletin for latest 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-7740C. 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
Navigate to router admin > Management > Remote Management > Disable
Restrict management access
allLimit management interface access to specific IP addresses
Navigate to router admin > Firewall > Access Control > Add rules to restrict management IPs
🧯 If You Can't Patch
- Isolate router on separate VLAN with strict firewall rules
- Implement network monitoring for suspicious backup function activity
🔍 How to Verify
Check if Vulnerable:
Check firmware version in router admin interface under System > FirmwareCheck Version:
Login to router web interface and navigate to System InformationVerify Fix Applied:
Verify firmware version matches or exceeds patched version from D-Link advisory📡 Detection & Monitoring
Log Indicators:
- Unusual backup operations
- Suspicious commands in system logs
- Multiple failed login attempts followed by backup activity
Network Indicators:
- Unexpected outbound connections from router
- Traffic to known malicious IPs from router
- Unusual backup file transfers
SIEM Query:
source="router_logs" AND (event="backup" OR event="configuration_change") AND user!="admin"