CVE-2026-6014 Overview
CVE-2026-6014 is a buffer overflow vulnerability in the D-Link DIR-513 router running firmware version 1.10. The flaw resides in the formAdvanceSetup function within /goform/formAdvanceSetup, part of the POST request handler. An attacker can manipulate the webpage argument to trigger memory corruption over the network. The exploit has been published publicly, increasing risk for exposed devices. D-Link no longer supports the affected hardware, so no official fix will be issued. Operators of legacy DIR-513 units must rely on compensating controls or device replacement to address the issue.
Critical Impact
Remote attackers with low-privileged authentication can corrupt router memory, potentially achieving code execution on an unsupported edge device that will not receive a vendor patch.
Affected Products
- D-Link DIR-513 router (hardware revision A2)
- D-Link DIR-513 firmware version 1.10
- End-of-life D-Link DIR-513 deployments still in production use
Discovery Timeline
- 2026-04-10 - CVE-2026-6014 published to NVD
- 2026-04-30 - Last updated in NVD database
Technical Details for CVE-2026-6014
Vulnerability Analysis
The vulnerability is a classic stack or heap buffer overflow [CWE-119] in the embedded web management interface of the DIR-513. When a POST request arrives at /goform/formAdvanceSetup, the formAdvanceSetup handler reads the webpage parameter without enforcing a maximum length. The handler copies the attacker-controlled value into a fixed-size buffer, overrunning adjacent memory. On MIPS-based SOHO routers like the DIR-513, this typically clobbers saved return addresses or function pointers, enabling control-flow hijacking. Because the device has reached end-of-life, the responsible maintainer will not publish firmware updates that correct the boundary check.
Root Cause
The root cause is improper restriction of operations within the bounds of a memory buffer. The formAdvanceSetup routine trusts the length of the webpage POST argument and performs an unchecked string copy into a static buffer. No input validation, length cap, or canary protection prevents the overflow, allowing adjacent stack or heap structures to be overwritten with attacker data.
Attack Vector
The attack is delivered remotely over the network to the router management interface. The attacker must hold low-level credentials to reach the authenticated handler, then submits a crafted POST request to /goform/formAdvanceSetup containing an oversized webpage value. Successful exploitation corrupts router memory, which can crash the device or be tuned to redirect execution. Devices exposing the management UI to the WAN are at the highest risk.
No verified proof-of-concept code is published in trusted repositories. The vulnerability mechanism is described in the VulDB Vulnerability Report #356570 and the Notion Setup Guide.
Detection Methods for CVE-2026-6014
Indicators of Compromise
- Unexpected reboots or crash loops on DIR-513 routers tied to inbound HTTP POST traffic.
- HTTP POST requests to /goform/formAdvanceSetup containing unusually long webpage parameter values.
- New or unexplained DNS, routing, or firewall rule changes on the affected router.
Detection Strategies
- Inspect web server and gateway logs for POST requests to /goform/formAdvanceSetup with payload sizes exceeding normal administrative traffic.
- Deploy network IDS signatures that flag oversized webpage form fields targeting D-Link goform endpoints.
- Correlate router crash telemetry with concurrent inbound HTTP traffic to identify exploitation attempts.
Monitoring Recommendations
- Forward router syslog and management-plane access logs to a central SIEM for retention and analysis.
- Alert on any management interface access originating from untrusted networks or non-administrative subnets.
- Track outbound connections from the router itself, which would be unusual for a SOHO gateway and may indicate post-exploitation activity.
How to Mitigate CVE-2026-6014
Immediate Actions Required
- Replace the DIR-513 with a currently supported router model, as D-Link will not issue a patch for this end-of-life device.
- Disable remote (WAN-side) administration on the router and restrict the management interface to a trusted LAN segment.
- Rotate the router administrator credentials and remove any unused accounts to limit authenticated attack paths.
- Place the router behind an upstream firewall that blocks unsolicited inbound HTTP traffic to the management port.
Patch Information
No patch is available. The vendor advisory page at D-Link Official Website lists the DIR-513 as a discontinued product outside its support lifecycle. Affected organizations must treat replacement as the primary remediation path.
Workarounds
- Segment the router onto an isolated VLAN and apply ACLs that permit management traffic only from a dedicated jump host.
- Front the management interface with a VPN, requiring tunnel authentication before any HTTP request reaches /goform/formAdvanceSetup.
- If the device must remain in service temporarily, monitor it continuously and prepare a rollback or replacement plan in case of compromise.
# Example upstream firewall rule to block WAN access to the DIR-513 management UI
# Replace <ROUTER_WAN_IP> with the device address and <TRUSTED_MGMT_CIDR> with your admin subnet
iptables -A FORWARD -p tcp -d <ROUTER_WAN_IP> --dport 80 -s <TRUSTED_MGMT_CIDR> -j ACCEPT
iptables -A FORWARD -p tcp -d <ROUTER_WAN_IP> --dport 80 -j DROP
iptables -A FORWARD -p tcp -d <ROUTER_WAN_IP> --dport 443 -s <TRUSTED_MGMT_CIDR> -j ACCEPT
iptables -A FORWARD -p tcp -d <ROUTER_WAN_IP> --dport 443 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
