CVE-2025-8949: D-Link DIR-825 Buffer Overflow Vulnerability

CVE-2025-8949 Overview

CVE-2025-8949 is a stack-based buffer overflow in the D-Link DIR-825 router running firmware version 2.10. The flaw resides in the get_ping_app_stat function of ping_response.cgi, served by the httpd component. Attackers manipulate the ping_ipaddr argument to overflow a fixed-size stack buffer and corrupt adjacent memory. The issue is remotely reachable over the network and the exploit details have been publicly disclosed. D-Link has confirmed that the DIR-825 2.10 is end-of-life and will not receive a fix, leaving exposed devices permanently vulnerable.

Critical Impact
Remote attackers can corrupt the httpd process stack on unsupported D-Link DIR-825 2.10 routers, potentially achieving arbitrary code execution on the device.

Affected Products

D-Link DIR-825 hardware router (end-of-life)
D-Link DIR-825 firmware version 2.10
ping_response.cgi handler within the httpd component

Discovery Timeline

2025-08-14 - CVE-2025-8949 published to NVD
2025-08-18 - Last updated in NVD database

Technical Details for CVE-2025-8949

Vulnerability Analysis

The vulnerability lives inside the get_ping_app_stat function of ping_response.cgi, a CGI handler exposed by the router's embedded httpd web server. The handler reads the user-supplied ping_ipaddr parameter from the HTTP request and copies it into a fixed-size stack buffer without enforcing length bounds. Supplying an oversized value overwrites the saved return address and adjacent stack data, classifying the flaw under [CWE-119] improper restriction of operations within the bounds of a memory buffer.

The EPSS score is 0.601% with a 69.66 percentile, indicating measurable exploitation interest relative to other CVEs. Because the affected hardware is no longer supported, residual exposure on the public internet will persist indefinitely.

Root Cause

The get_ping_app_stat routine performs an unbounded string copy of attacker-controlled input into a local stack buffer. The CGI code does not validate the length or format of ping_ipaddr before passing it to the copy operation. Embedded MIPS firmware of this generation typically lacks stack canaries and address space layout randomization (ASLR), removing the standard mitigations that would otherwise complicate exploitation.

Attack Vector

An authenticated attacker with administrative access to the router's web interface sends a crafted HTTP request to ping_response.cgi with an oversized ping_ipaddr parameter. The request triggers the overflow inside the httpd process running on the device. The CVSS 4.0 vector requires high privileges, which constrains the attack to scenarios where credentials are known, default, reused, or obtained through chained vulnerabilities.

A verified proof-of-concept exploit was not published in the references; the vulnerability mechanics are described in the GitHub CVE Issue Discussion and VulDB #319915. No vendor patch exists because the product is out of support.

Detection Methods for CVE-2025-8949

Indicators of Compromise

HTTP POST or GET requests to /ping_response.cgi containing unusually long ping_ipaddr values or non-IP-format payloads.
Unexpected httpd process crashes, restarts, or watchdog reboots on DIR-825 devices.
Outbound connections initiated by the router to unknown hosts following a web-interface request burst.

Detection Strategies

Inspect HTTP traffic to router management interfaces for requests targeting ping_response.cgi with ping_ipaddr parameters exceeding standard IPv4 string length.
Apply network IDS signatures that match overlong query strings against legacy D-Link CGI endpoints.
Correlate router log entries showing repeated authentication followed by ping diagnostic calls.

Monitoring Recommendations

Forward router syslog and authentication events to a centralized logging platform for anomaly review.
Alert on management-plane access from unexpected source addresses or geographies.
Track DNS and outbound traffic patterns originating from the router subnet to identify post-compromise activity.

How to Mitigate CVE-2025-8949

Immediate Actions Required

Retire D-Link DIR-825 2.10 devices and replace them with a supported router, since no patch will be released.
Disable remote (WAN-side) management of the web interface on any DIR-825 still in service.
Rotate administrative credentials and enforce strong, unique passwords to raise the bar against the privilege precondition.
Segment the router's management interface onto a restricted VLAN accessible only from trusted hosts.

Patch Information

No patch is available. D-Link's advisory for end-of-life hardware directs customers to replace the device. Refer to the D-Link Security Homepage for end-of-life guidance and successor product recommendations.

Workarounds

Block external access to TCP ports 80 and 443 on the router's WAN interface at the upstream firewall.
Restrict LAN-side access to /ping_response.cgi via access control lists where the device firmware permits.
Monitor and rate-limit HTTP requests to the router's diagnostic CGI endpoints from internal segments.

bash

# Example upstream firewall rules to block WAN management access to an EOL DIR-825
iptables -A FORWARD -p tcp -d <router_wan_ip> --dport 80  -j DROP
iptables -A FORWARD -p tcp -d <router_wan_ip> --dport 443 -j DROP
iptables -A FORWARD -p tcp -d <router_wan_ip> --dport 8080 -j DROP