CVE-2025-2553: D-Link DIR-618 Auth Bypass Vulnerability

CVE-2025-2553 Overview

CVE-2025-2553 is an improper access control vulnerability affecting D-Link DIR-618 firmware version 2.02 and DIR-605L firmware version 3.02. The flaw resides in the /goform/formVirtualServ endpoint, which handles virtual server (port forwarding) configuration on the affected routers. An attacker on the adjacent network can manipulate the endpoint to alter access-controlled settings without proper authorization. The vulnerability is classified under [CWE-266: Incorrect Privilege Assignment]. Both affected devices are end-of-life and no longer receive security updates from D-Link. The exploit details have been publicly disclosed, increasing the risk of opportunistic attacks against exposed devices.

Critical Impact
An adjacent attacker can modify virtual server (port forwarding) configuration on affected D-Link routers without proper authorization, potentially exposing internal network services to the internet.

Affected Products

D-Link DIR-618 (firmware 2.02) — end-of-life
D-Link DIR-605L (firmware 3.02) — end-of-life
Vulnerable component: /goform/formVirtualServ handler

Discovery Timeline

2025-03-20 - CVE-2025-2553 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-2553

Vulnerability Analysis

The vulnerability affects the HTTP handler at /goform/formVirtualServ in the D-Link DIR-618 and DIR-605L web administration interfaces. This handler processes virtual server (port forwarding) rule submissions. The handler fails to enforce proper access control checks before applying configuration changes. As a result, an attacker positioned on the adjacent network (typically the local LAN or Wi-Fi segment) can invoke the endpoint and manipulate port forwarding rules. Modifying these rules can expose internal hosts and services to untrusted networks, undermining the router's perimeter role. Because both devices are end-of-life, no vendor patch will be issued.

Root Cause

The root cause is missing or insufficient authorization enforcement in the formVirtualServ request handler [CWE-266]. The endpoint accepts and processes state-changing requests without verifying that the requester holds appropriate privileges for modifying virtual server configuration. This class of flaw is common in older SOHO router firmware where administrative form handlers rely on client-side or session assumptions rather than server-side authorization checks.

Attack Vector

Exploitation requires network adjacency: the attacker must reach the router's HTTP administration interface from the same local network segment. This can occur through a compromised device on the LAN, an untrusted guest client, or an attacker who has joined the Wi-Fi network. Once reachable, the attacker submits crafted requests to /goform/formVirtualServ to alter port forwarding entries. Attack complexity is low and no user interaction is required. Public disclosure of the technique lowers the barrier for opportunistic exploitation.

No verified proof-of-concept code is included here. Refer to the VulDB entry #300167 and the researcher notes for DIR-618 and DIR-605L for technical details.

Detection Methods for CVE-2025-2553

Indicators of Compromise

Unexpected entries in the router's Virtual Server / Port Forwarding configuration.
HTTP POST requests to /goform/formVirtualServ originating from unauthenticated or unexpected LAN clients.
Inbound WAN connection attempts to internal hosts on ports that administrators did not intentionally forward.
Router configuration changes occurring outside of scheduled administrative windows.

Detection Strategies

Capture and inspect HTTP traffic on the LAN targeting the router management IP for requests to /goform/formVirtualServ.
Periodically export and diff the router's port forwarding configuration to identify unauthorized changes.
Alert on any newly opened inbound ports observed at the WAN edge that do not correspond to approved forwarding rules.

Monitoring Recommendations

Forward router syslog and administrative events to a centralized logging or SIEM platform for review.
Monitor DHCP and ARP tables for unauthorized clients on the LAN and Wi-Fi segments adjacent to the router.
Track inbound scanning activity against the router's WAN IP that aligns with newly created virtual server entries.

How to Mitigate CVE-2025-2553

Immediate Actions Required

Replace end-of-life D-Link DIR-618 and DIR-605L devices with a currently supported router model.
Restrict access to the router's web administration interface to trusted management hosts only.
Audit existing virtual server / port forwarding rules and remove any entries that are not explicitly required.
Change the router administrator password and disable remote (WAN-side) management if enabled.

Patch Information

D-Link has confirmed that the DIR-618 and DIR-605L are no longer supported and will not receive a fix for CVE-2025-2553. Consult the D-Link official website for current product lifecycle information and supported replacement devices. Organizations must plan hardware replacement as the primary remediation path.

Workarounds

Segment vulnerable routers onto an isolated network with no untrusted clients until they can be replaced.
Disable the router's web administration interface on wireless interfaces where feasible.
Enforce strong Wi-Fi authentication (WPA2/WPA3 with a long passphrase) to limit adjacent-network exposure.
Place a supported firewall in front of the affected device and block unsolicited inbound WAN traffic.

bash

# Example: block LAN client access to the router admin interface
# from an upstream firewall (adjust interfaces and router IP)
iptables -I FORWARD -s 192.168.0.0/24 -d 192.168.0.1 -p tcp \
    --dport 80 -m conntrack --ctstate NEW -j DROP
iptables -I FORWARD -s 192.168.0.0/24 -d 192.168.0.1 -p tcp \
    --dport 443 -m conntrack --ctstate NEW -j DROP