CVE-2025-4345: D-Link DIR-600L Buffer Overflow Vulnerability

CVE-2025-4345 Overview

CVE-2025-4345 is a buffer overflow vulnerability in the D-Link DIR-600L wireless router firmware up to version 2.07B01. The flaw resides in the formSetLog function, where improper handling of the host argument allows an attacker to overflow a fixed-size buffer. The vulnerability is remotely exploitable over the network and affects a product line that D-Link no longer supports with security updates.

The weakness is classified under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer) and [CWE-120] (Classic Buffer Overflow). Because the affected device has reached end-of-life, no vendor patch will be released for affected hardware.

Critical Impact
Remote attackers with low-privilege access can trigger a buffer overflow in formSetLog, potentially leading to arbitrary code execution or denial of service on unsupported D-Link DIR-600L routers.

Affected Products

D-Link DIR-600L router (hardware, end-of-life)
D-Link DIR-600L firmware versions up to and including 2.07B01
All deployments still operating unsupported DIR-600L devices in production

Discovery Timeline

2025-05-06 - CVE-2025-4345 published to the National Vulnerability Database (NVD)
2025-05-12 - Last updated in NVD database

Technical Details for CVE-2025-4345

Vulnerability Analysis

The vulnerability affects the formSetLog handler exposed by the DIR-600L web management interface. When an authenticated request is processed, the host parameter is copied into a stack or heap buffer without proper length validation. An attacker who submits an oversized host value can overwrite adjacent memory, corrupting control structures such as saved return addresses or function pointers.

With an EPSS score of 1.153% (78th percentile), the vulnerability ranks above the majority of CVEs for near-term exploitation likelihood. No public exploit has been observed in the wild, and the issue is not listed in the CISA Known Exploited Vulnerabilities catalog.

Root Cause

The root cause is a classic buffer overflow [CWE-120]. The formSetLog function fails to validate or bound the length of the user-supplied host argument before writing it into a fixed-size buffer. Embedded routers like the DIR-600L commonly use unchecked string operations such as strcpy or sprintf in CGI handlers. The absence of stack canaries and address space layout randomization (ASLR) in this generation of D-Link firmware increases the reliability of memory corruption exploitation.

Attack Vector

The attack vector is network-based and requires low privileges, typically meaning an authenticated session to the router web interface. An attacker reaches the vulnerable endpoint by sending a crafted HTTP POST request to the formSetLog handler with an oversized host parameter. Routers exposing the management interface to the WAN or shared LAN segments are at highest risk. Successful exploitation can yield remote code execution as the web service account, which on consumer routers typically runs with root-equivalent privileges.

A proof-of-concept describing the parameter manipulation is published in the GitHub PoC Repository and tracked as VulDB #307463.

Detection Methods for CVE-2025-4345

Indicators of Compromise

HTTP POST requests to the router management interface targeting formSetLog with abnormally long host parameter values
Unexpected reboots, crashes, or httpd process restarts on DIR-600L devices coinciding with inbound web requests
Outbound connections from the router to unfamiliar hosts, indicating possible post-exploitation command-and-control activity
New or modified firewall, DNS, or routing rules on the affected device

Detection Strategies

Inspect network traffic for HTTP requests to /goform/formSetLog containing oversized parameter values exceeding typical hostname lengths
Deploy intrusion detection signatures that flag long-string overflow patterns directed at D-Link CGI endpoints
Correlate router syslog events with perimeter logs to identify probe sequences against legacy management URIs

Monitoring Recommendations

Continuously monitor for any DIR-600L devices still present in the asset inventory and flag them as end-of-life
Alert on management interface access from non-administrative source networks
Capture and review packet metadata for traffic destined to the router's HTTP management port from internal hosts

How to Mitigate CVE-2025-4345

Immediate Actions Required

Replace D-Link DIR-600L devices with currently supported router models, as the product is end-of-life and will not receive a patch
Disable remote (WAN-side) management access on any DIR-600L still in service
Restrict administrative access to the router web interface to a dedicated management VLAN or trusted host
Rotate router administrative credentials and audit configured accounts for unauthorized changes

Patch Information

No patch is available. D-Link has confirmed the DIR-600L is no longer supported by the maintainer, and the vendor will not issue firmware updates for this hardware. Refer to the D-Link Official Website for current end-of-life guidance and replacement product lines. Additional vulnerability context is available at VulDB CTI #307463.

Workarounds

Segment the affected router behind a supported firewall and block inbound access to its HTTP management port
Place the device on an isolated VLAN with no access to sensitive internal resources
Decommission the device entirely where replacement is feasible — segmentation only reduces, not eliminates, exposure
Monitor the network segment hosting the device for anomalous outbound connections that may indicate compromise

bash

# Example: block external access to the router's HTTP management interface
# Replace ROUTER_IP with the DIR-600L LAN address
iptables -A FORWARD -p tcp -d ROUTER_IP --dport 80 -m iprange ! --src-range 10.0.0.10-10.0.0.20 -j DROP
iptables -A FORWARD -p tcp -d ROUTER_IP --dport 443 -m iprange ! --src-range 10.0.0.10-10.0.0.20 -j DROP