CVE-2025-70246 Overview
CVE-2025-70246 is a stack-based buffer overflow [CWE-121] in the D-Link DIR-513 router running firmware version 1.10. The flaw resides in the goform/formVirtualServ handler, where the curTime parameter is copied into a fixed-size stack buffer without proper bounds checking. Remote, unauthenticated attackers can send a crafted HTTP request to corrupt the stack and crash the device. The DIR-513 is an end-of-life consumer router, and no patched firmware is available from D-Link for this product line.
Critical Impact
Unauthenticated network attackers can trigger a denial of service on affected DIR-513 routers by overflowing the stack buffer through the curTime parameter.
Affected Products
- D-Link DIR-513 hardware (all units running the vulnerable firmware)
- D-Link DIR-513 firmware version 1.10
- End-of-life consumer wireless router product line
Discovery Timeline
- 2026-03-10 - CVE-2025-70246 published to the National Vulnerability Database
- 2026-03-11 - Last updated in NVD database
Technical Details for CVE-2025-70246
Vulnerability Analysis
The vulnerability exists in the DIR-513 web administration interface, specifically in the formVirtualServ form handler exposed at the goform/formVirtualServ endpoint. This endpoint processes virtual server (port forwarding) configuration requests submitted from the router's management UI. The handler accepts a curTime parameter and writes it into a stack-allocated buffer without enforcing a maximum length.
When an attacker supplies an oversized curTime value, the copy operation overruns the destination buffer and corrupts adjacent stack memory, including the saved return address. The result is a process crash and reboot of the router's HTTP daemon. Because the DIR-513 is a MIPS-based embedded device without modern exploit mitigations such as ASLR or stack canaries on the affected service, return address corruption could potentially be leveraged for code execution, though the CVSS impact only reflects high availability impact.
Root Cause
The root cause is the use of an unsafe string copy operation (such as strcpy or sprintf) on attacker-controlled input from the HTTP request body. The formVirtualServ handler trusts the length of the curTime parameter and fails to validate or truncate it before storage. This pattern is common in legacy D-Link goform handlers compiled from the Boa or similar embedded webserver framework.
Attack Vector
The attack vector is network-based and requires no authentication or user interaction. An attacker with network reachability to the router's web management interface (typically TCP port 80 on the LAN, or WAN if remote administration is enabled) sends an HTTP POST request to /goform/formVirtualServ containing an oversized curTime parameter. Successful exploitation crashes the embedded HTTP server, denying access to management functions and potentially disrupting routing services. Public proof-of-concept details are referenced in the GitHub CVE-2025-70246 Report.
Detection Methods for CVE-2025-70246
Indicators of Compromise
- HTTP POST requests to /goform/formVirtualServ containing abnormally long curTime parameter values.
- Unexpected reboots or HTTP daemon crashes on DIR-513 devices following inbound web management traffic.
- Repeated TCP connections to the router's management port from a single external or LAN-side source.
Detection Strategies
- Inspect HTTP request payloads destined for DIR-513 management interfaces for curTime parameter values exceeding typical timestamp lengths.
- Deploy network IDS signatures that flag long string parameters submitted to goform/* endpoints on D-Link devices.
- Correlate router availability loss events with preceding HTTP traffic to identify exploitation attempts.
Monitoring Recommendations
- Log all HTTP requests reaching consumer router management interfaces from upstream segments.
- Monitor SNMP or syslog output from the DIR-513 for repeated process restart events.
- Alert on any inbound WAN connections to the router's HTTP administration port.
How to Mitigate CVE-2025-70246
Immediate Actions Required
- Disable remote (WAN-side) web administration on DIR-513 devices to remove external exposure.
- Restrict LAN access to the router management interface to a dedicated administrative VLAN or trusted host.
- Replace end-of-life DIR-513 hardware with a currently supported router, as D-Link no longer issues firmware updates for this model.
Patch Information
No vendor patch is available. The DIR-513 is a legacy product, and D-Link directs customers to the D-Link Security Bulletin for end-of-life advisories. Confirm device end-of-life status against the D-Link Product Support Info page before planning replacement.
Workarounds
- Block inbound traffic to TCP port 80 and 443 on the router's WAN interface via upstream firewall rules.
- Place the DIR-513 behind a network segment that filters HTTP access to its management endpoints.
- Disable the virtual server (port forwarding) configuration UI exposure through ACLs where the firmware supports it.
# Configuration example: upstream firewall ACL blocking WAN access to DIR-513 management
iptables -A FORWARD -p tcp -d <DIR-513-WAN-IP> --dport 80 -j DROP
iptables -A FORWARD -p tcp -d <DIR-513-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.
