CVE-2025-29515 Overview
CVE-2025-29515 is a critical Broken Access Control vulnerability affecting the D-Link DSL-7740C router with firmware version DSL7740C.V6.TR069.20211230. The vulnerability exists in the DELT_file.xgi endpoint, which fails to properly enforce access controls, allowing unauthenticated remote attackers to modify arbitrary settings within the device's XML database. Most critically, this includes the ability to change the administrator password, enabling complete device takeover.
Critical Impact
Unauthenticated attackers can remotely compromise D-Link DSL-7740C routers by modifying the administrator password and taking full control of the device without any prior authentication.
Affected Products
- D-Link DSL-7740C Firmware Version 6.TR069.20211230
- D-Link DSL-7740C Hardware Device
Discovery Timeline
- 2025-08-25 - CVE-2025-29515 published to NVD
- 2025-09-02 - Last updated in NVD database
Technical Details for CVE-2025-29515
Vulnerability Analysis
This vulnerability stems from improper access control (CWE-284) in the D-Link DSL-7740C router's web management interface. The DELT_file.xgi endpoint lacks proper authentication and authorization checks, allowing any network-accessible attacker to directly interact with the device's internal XML configuration database.
The attack requires no authentication, no user interaction, and can be executed remotely over the network. Successful exploitation grants attackers complete control over the device, including the ability to modify administrator credentials, change network configurations, intercept traffic, or use the compromised router as a pivot point for further attacks.
Root Cause
The root cause is a missing access control enforcement mechanism in the DELT_file.xgi CGI endpoint. The endpoint processes requests to delete or modify XML database entries without first verifying that the requesting party has appropriate privileges. This allows unauthenticated users to perform actions that should be restricted to authenticated administrators only.
Attack Vector
The attack is network-based and can be executed by any attacker who can reach the router's web management interface. In typical deployments where the management interface is accessible from the local network, an attacker on the same network segment can exploit this vulnerability. If the management interface is exposed to the internet (which is sometimes the case with ISP-provided equipment), the attack surface extends to any remote attacker.
The attacker sends specially crafted HTTP requests to the DELT_file.xgi endpoint, specifying the XML database entries to modify. By targeting the administrator password configuration, the attacker can set a known password and subsequently log in with full administrative access.
Technical details and proof-of-concept information are available in the GitHub Gist PoC published by the security researcher.
Detection Methods for CVE-2025-29515
Indicators of Compromise
- Unexpected HTTP requests to the /DELT_file.xgi endpoint in router access logs
- Unauthorized changes to administrator credentials or router configuration
- Unusual login activity from unknown IP addresses to the router management interface
- Modified XML database entries without corresponding authorized administrative actions
Detection Strategies
- Monitor network traffic for HTTP requests targeting /DELT_file.xgi on port 80 or the router's management port
- Implement intrusion detection rules to alert on unauthenticated requests to CGI endpoints on network infrastructure devices
- Deploy network segmentation to isolate router management interfaces and monitor cross-segment traffic
- Review router access logs regularly for signs of unauthorized configuration changes
Monitoring Recommendations
- Enable and centralize logging from D-Link router devices where possible
- Configure alerts for any changes to administrative credentials on network devices
- Implement network monitoring solutions capable of detecting anomalous traffic patterns to router management interfaces
- Use SentinelOne Singularity to monitor endpoints for post-exploitation activity that may originate from compromised network devices
How to Mitigate CVE-2025-29515
Immediate Actions Required
- Restrict access to the router's web management interface to trusted IP addresses only
- Disable remote management access from WAN/internet-facing interfaces
- Implement network segmentation to isolate router management interfaces from general network traffic
- Monitor for unauthorized access attempts and configuration changes
- Check the D-Link Security Bulletin for firmware updates addressing this vulnerability
Patch Information
D-Link has published information regarding this vulnerability in their security bulletin. Affected users should consult the D-Link Security Bulletin page for the latest firmware updates and security guidance. Given that the affected firmware version dates from December 2021, users should verify whether their device is still supported and whether a patched firmware version is available.
If the device is no longer supported by D-Link, users should strongly consider replacing the device with a currently supported model that receives security updates.
Workarounds
- Disable the web-based management interface entirely if not required for operations
- Configure firewall rules to block external access to the router's management interface on ports 80 and 443
- Use VPN or out-of-band management networks for router administration
- Regularly verify that administrator credentials have not been modified by checking against known-good values
- Consider replacing end-of-life devices that no longer receive security updates from the vendor
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
