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

CVE-2025-7206 Overview

CVE-2025-7206 is a stack-based buffer overflow vulnerability in the D-Link DIR-825 wireless router running firmware version 2.10. The flaw resides in the sub_410DDC function inside the switch_language.cgi script handled by the httpd component. Attackers can manipulate the Language argument to overflow a fixed-size stack buffer. The vulnerability is reachable over the network without authentication. The exploit details have been disclosed publicly, increasing the risk of opportunistic attacks. D-Link has confirmed that the DIR-825 2.10 is end-of-life and will not receive a security patch.

Critical Impact
Unauthenticated remote attackers can corrupt stack memory in the embedded web server, potentially leading to arbitrary code execution or device compromise on affected routers.

Affected Products

D-Link DIR-825 hardware router (end-of-life)
D-Link DIR-825 firmware version 2.10
httpd component handling switch_language.cgi

Discovery Timeline

2025-07-09 - CVE-2025-7206 published to NVD
2025-07-14 - Last updated in NVD database

Technical Details for CVE-2025-7206

Vulnerability Analysis

The vulnerability is a classic stack-based buffer overflow [CWE-119] in the embedded httpd web server of the D-Link DIR-825. The affected function sub_410DDC processes the Language parameter from the switch_language.cgi endpoint. The function copies the user-supplied value into a fixed-size stack buffer without enforcing length boundaries. An attacker who supplies an oversized Language value overruns the buffer and overwrites adjacent stack data, including the saved return address.

Because the request reaches the router's web interface directly, exploitation does not require credentials or user interaction. The MIPS-based firmware typically lacks modern exploit mitigations such as Address Space Layout Randomization (ASLR) and stack canaries, which simplifies reliable exploitation. Successful exploitation grants control over the httpd process, which on consumer routers commonly runs with elevated privileges. The product line is no longer supported, so no vendor patch is forthcoming.

Root Cause

The root cause is unsafe handling of attacker-controlled input inside sub_410DDC. The function reads the Language parameter from the HTTP request and writes it into a fixed stack buffer using an unbounded copy routine. The absence of length validation against the buffer size allows memory corruption beyond the buffer boundary.

Attack Vector

An attacker sends a crafted HTTP request to the switch_language.cgi endpoint exposed by the router's httpd service. The Language parameter contains a payload longer than the destination buffer. Exposure of the management interface to the LAN or, in misconfigured deployments, the WAN side determines reachability. Public disclosure of exploit details increases the likelihood of weaponization.

No verified proof-of-concept code is published in this advisory. See the GitHub CVE Issue Report and VulDB entry #315155 for technical details on the disclosed exploitation path.

Detection Methods for CVE-2025-7206

Indicators of Compromise

HTTP requests to /switch_language.cgi containing an unusually long Language parameter value
Unexpected httpd process crashes or restarts on the router
Outbound connections from the router to unfamiliar external hosts following targeted web requests
New or modified firmware-level configuration changes without administrator action

Detection Strategies

Inspect network traffic destined for the router management interface for oversized query strings or POST bodies targeting switch_language.cgi
Apply intrusion detection signatures that flag Language= parameters exceeding a reasonable character length
Correlate router availability dips with preceding HTTP requests to the httpd interface

Monitoring Recommendations

Forward router syslog and access logs to a centralized log platform for retention and analysis
Alert on any external source attempting to access router administrative endpoints
Track baseline behavior of the httpd service and alert on repeated termination or restart events

How to Mitigate CVE-2025-7206

Immediate Actions Required

Replace the D-Link DIR-825 with a supported router model, as the device is end-of-life and will not receive a fix
Disable remote (WAN-side) administration on the router immediately
Restrict LAN access to the management interface to a dedicated administrative network segment
Audit network exposure of the device and remove any port-forwarding rules that expose httpd

Patch Information

No patch is available. D-Link has confirmed that the DIR-825 2.10 is no longer supported. Refer to D-Link Security Information for end-of-life guidance and supported replacement models.

Workarounds

Place the router behind a network segmentation boundary that blocks untrusted hosts from reaching the management interface
Filter HTTP traffic to switch_language.cgi at an upstream firewall or web filter
Decommission the device and migrate to a vendor-supported router that receives security updates

bash

# Example firewall rule to block external access to the router admin interface
iptables -A INPUT -p tcp --dport 80 -i wan0 -j DROP
iptables -A INPUT -p tcp --dport 443 -i wan0 -j DROP