CVE-2025-7206: D-Link DIR-825 Buffer Overflow Vulnerability

CVE-2025-7206 Overview

A critical stack-based buffer overflow vulnerability has been identified in the D-Link DIR-825 router firmware version 2.10. This vulnerability exists within the sub_410DDC function of the switch_language.cgi file, which is part of the httpd component. The vulnerability is triggered through improper handling of the Language argument, allowing remote attackers to exploit the buffer overflow condition without authentication.

Critical Impact

Remote attackers can exploit this stack-based buffer overflow to potentially execute arbitrary code, crash the device, or gain unauthorized control over affected D-Link DIR-825 routers. This vulnerability affects end-of-life products no longer supported by the vendor.

Affected Products

• D-Link DIR-825 Firmware version 2.10
• D-Link DIR-825 Hardware

Discovery Timeline

• July 9, 2025 - CVE-2025-7206 published to NVD
• July 14, 2025 - Last updated in NVD database

Technical Details for CVE-2025-7206

Vulnerability Analysis

This vulnerability is a stack-based buffer overflow (CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer) that affects the web management interface of the D-Link DIR-825 router. The vulnerability resides in the httpd service, specifically within the CGI handler for language switching functionality.

When processing HTTP requests to switch_language.cgi, the sub_410DDC function fails to properly validate the length of user-supplied input for the Language parameter. This allows an attacker to submit a crafted request with an oversized Language value that exceeds the allocated stack buffer, leading to memory corruption.

The network-accessible nature of this vulnerability means that any attacker who can reach the router's web interface can exploit this flaw without requiring any authentication or user interaction. Successful exploitation could allow an attacker to overwrite return addresses on the stack, potentially redirecting execution flow to attacker-controlled code.

Root Cause

The root cause is insufficient bounds checking in the sub_410DDC function when processing the Language argument from user input. The function allocates a fixed-size buffer on the stack but fails to validate that the input length does not exceed this buffer size before copying data, resulting in a classic stack-based buffer overflow condition.

Attack Vector

The attack is network-based and can be initiated remotely against the router's web management interface. An attacker would craft a malicious HTTP request to the switch_language.cgi endpoint with an oversized Language parameter value. Since the vulnerability exists in the httpd component that handles web requests, any network-accessible D-Link DIR-825 running vulnerable firmware is at risk.

The exploitation path involves sending a specially crafted HTTP request containing a Language parameter with content designed to overflow the stack buffer. This overflow can corrupt adjacent stack memory, including saved return addresses, potentially enabling arbitrary code execution in the context of the httpd process.

For detailed technical information about the vulnerability mechanism, refer to the GitHub CVE Issue Tracker and VulDB entry #315155.

Detection Methods for CVE-2025-7206

Indicators of Compromise

• Anomalous HTTP requests to switch_language.cgi with unusually long Language parameter values
• Unexpected crashes or restarts of the httpd service on D-Link DIR-825 devices
• Evidence of memory corruption or buffer overflow patterns in router logs
• Unusual outbound network connections from the router indicating potential compromise

Detection Strategies

• Implement network intrusion detection rules to monitor for oversized HTTP parameters targeting switch_language.cgi
• Deploy deep packet inspection to identify malformed requests with buffer overflow payloads
• Monitor web server logs for repeated requests to switch_language.cgi with abnormal parameter lengths
• Utilize SentinelOne Singularity for network traffic analysis to detect exploitation attempts

Monitoring Recommendations

• Enable verbose logging on D-Link DIR-825 devices where possible to capture anomalous activity
• Set up alerts for HTTP 500 errors or service crashes associated with the httpd component
• Monitor network traffic patterns for reconnaissance activity targeting router management interfaces
• Implement SIEM correlation rules to detect multiple failed exploitation attempts

How to Mitigate CVE-2025-7206

Immediate Actions Required

• Restrict network access to the router's web management interface to trusted IP addresses only
• Disable remote management features if not required
• Implement firewall rules to block external access to the router's administrative ports
• Consider replacing the affected device with a supported model as this product is end-of-life

Patch Information

This vulnerability affects a product that is no longer supported by D-Link. As an end-of-life device, the DIR-825 will not receive security patches for this vulnerability. Users are strongly advised to replace the affected hardware with currently supported D-Link models or alternative router solutions. For more information, visit the D-Link Official Website.

Workarounds

• Disable the web management interface entirely and use only local console access if available
• Segment the network to isolate vulnerable routers from untrusted networks
• Implement a web application firewall (WAF) to filter malicious requests before they reach the device
• Use VPN access to reach the management interface rather than exposing it directly

# Example: Restrict access to router management interface via upstream firewall
# Block external access to common router management ports
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -j DROP
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 443 -j DROP

# Allow management access only from specific trusted IP
iptables -I FORWARD -s 192.168.1.100 -d 192.168.1.1 -p tcp --dport 80 -j ACCEPT