CVE-2025-2548: D-Link DIR-618 Auth Bypass Vulnerability

CVE-2025-2548 Overview

CVE-2025-2548 is an improper access control vulnerability affecting D-Link DIR-618 and DIR-605L 2.02/3.02 routers. The flaw resides in an unspecified function of the /goform/formSetDomainFilter endpoint. Attackers on the local network can manipulate the endpoint to bypass intended access restrictions on the device's domain filter configuration. The vulnerability is classified under [CWE-266] (Incorrect Privilege Assignment). Both affected models reached end-of-life status, and D-Link will not release fixes. Public disclosure has occurred through VulDB submission #516790, increasing the likelihood of opportunistic exploitation against exposed legacy devices.

Critical Impact
Adjacent-network attackers can manipulate domain filter settings on unsupported D-Link DIR-618 and DIR-605L routers, undermining network access controls. No vendor patch will be issued.

Affected Products

D-Link DIR-618 (firmware version 2.02)
D-Link DIR-605L (firmware version 3.02)
All hardware revisions of the above models — both products are end-of-life

Discovery Timeline

2025-03-20 - CVE-2025-2548 published to NVD
2025-07-15 - Last updated in NVD database

Technical Details for CVE-2025-2548

Vulnerability Analysis

The vulnerability affects the formSetDomainFilter handler in the device's goform web management interface. This handler processes requests to configure the router's domain filtering policy, which controls which domains clients on the LAN can reach. The handler fails to enforce proper access controls, allowing unauthorized requests to modify filter rules. An attacker on the same broadcast domain — for example, a guest Wi-Fi client or a compromised internal host — can issue crafted HTTP requests to the endpoint without proper authorization. The result is integrity loss on the device's filtering configuration, which can be used to disable parental controls, redirect blocked categories, or weaken network segmentation policies enforced by the router. Because both DIR-618 and DIR-605L are no longer supported, the affected code path will remain unpatched in the firmware images currently deployed by users. Refer to the Notion Security Analysis for DIR-618 and the Notion Security Analysis for DIR-605L for additional technical context.

Root Cause

The root cause is missing or insufficient privilege validation within the /goform/formSetDomainFilter handler. The router accepts and processes configuration-changing requests without verifying that the requestor holds administrative privileges, mapping to [CWE-266] Incorrect Privilege Assignment.

Attack Vector

Exploitation requires adjacent-network access — the attacker must be on the same Layer 2 segment as the router's LAN interface. The attack requires no authentication and no user interaction. Public disclosure through VulDB #300162 provides enough detail for adversaries to reproduce the attack.

No verified exploit code is available in public repositories. The vulnerability mechanism is described in the referenced advisories above; readers should consult those sources for protocol-level reproduction details rather than synthetic examples.

Detection Methods for CVE-2025-2548

Indicators of Compromise

Unexpected HTTP POST requests to /goform/formSetDomainFilter originating from non-administrator hosts on the LAN.
Domain filter rule entries on the router that were not created by an administrator, or filter policies reverting after legitimate updates.
Sudden ability of internal clients to reach domains previously blocked by router policy.

Detection Strategies

Capture and inspect LAN-side HTTP traffic destined for the router's management interface and alert on formSetDomainFilter requests from non-admin IPs.
Periodically audit the router's domain filter ruleset against a known-good baseline configuration.
Monitor router system logs, where available, for configuration change events outside scheduled maintenance windows.

Monitoring Recommendations

Place legacy D-Link routers behind a managed firewall and log all traffic to their management interface.
Forward LAN telemetry to a centralized log platform and alert on administrative endpoint access from client VLANs.
Track EPSS movement for CVE-2025-2548 (currently 0.436%, 63rd percentile) as a signal of changing exploitation interest.

How to Mitigate CVE-2025-2548

Immediate Actions Required

Replace affected DIR-618 and DIR-605L devices with a currently supported router model, since both products are end-of-life.
If immediate replacement is not feasible, isolate the router's LAN interface from untrusted clients using VLAN segmentation.
Restrict access to the router's web management interface to a single administrative host via firewall rules where the device supports it.
Disable the domain filter feature if it is not actively used, reducing the attack surface of the formSetDomainFilter handler.

Patch Information

D-Link has confirmed that DIR-618 and DIR-605L are no longer supported. No firmware patch will be released for CVE-2025-2548. The official product status is published on the D-Link Official Website. Migration to a supported platform is the only complete remediation.

Workarounds

Segment legacy routers onto a dedicated VLAN with no untrusted clients and block lateral access to the management interface.
Enforce strong WPA2/WPA3 credentials and disable guest networks to limit who can reach the LAN-side management surface.
Use upstream DNS filtering or a network firewall to enforce domain policy independently of the router's built-in filter.

bash

# Example upstream firewall rule restricting management access to a single admin host
# (syntax depends on firewall vendor — adapt accordingly)
iptables -A FORWARD -d 192.168.0.1 -p tcp --dport 80 -s 192.168.0.10 -j ACCEPT
iptables -A FORWARD -d 192.168.0.1 -p tcp --dport 80 -j DROP