CVE-2025-70251 Overview
CVE-2025-70251 is a stack buffer overflow vulnerability [CWE-121] affecting the D-Link DIR-513 router firmware version 1.10. The flaw resides in the goform/formWlanGuestSetup handler, which fails to properly validate the length of the webPage parameter before copying it into a fixed-size stack buffer. Remote, unauthenticated attackers can exploit the issue across the network to crash the device and disrupt wireless service.
Critical Impact
Remote unauthenticated attackers can trigger a denial-of-service condition on affected D-Link DIR-513 routers by sending an oversized webPage parameter to the guest Wi-Fi configuration endpoint.
Affected Products
- D-Link DIR-513 router (hardware)
- D-Link DIR-513 firmware version 1.10
- Deployments exposing the web management interface on the LAN or WAN
Discovery Timeline
- 2026-03-10 - CVE-2025-70251 published to the National Vulnerability Database (NVD)
- 2026-03-11 - Last updated in NVD database
Technical Details for CVE-2025-70251
Vulnerability Analysis
The D-Link DIR-513 web management interface exposes the formWlanGuestSetup action under the goform/ endpoint. This handler processes guest wireless network configuration submitted from the administrative UI. The handler reads the webPage HTTP parameter and copies it into a fixed-length buffer allocated on the stack without enforcing a length check.
When an attacker submits a webPage value that exceeds the destination buffer size, the copy operation writes past the buffer boundary. The overflow corrupts adjacent stack data, including saved registers and the function return address. On the MIPS-based DIR-513, this corruption reliably crashes the httpd process and forces the device to reboot.
The vulnerability is reachable over the network without authentication or user interaction, consistent with the unauthenticated attack surface common to legacy SOHO routers. The DIR-513 is an end-of-life consumer product, and D-Link directs customers to the vendor security bulletin for handling guidance.
Root Cause
The root cause is the absence of bounds checking on attacker-controlled input before invoking an unsafe string copy into a stack-resident buffer. The handler trusts the webPage parameter length supplied through the HTTP request, violating CWE-121 (Stack-based Buffer Overflow) safe-coding practices.
Attack Vector
An attacker sends a crafted HTTP request to goform/formWlanGuestSetup containing an oversized webPage parameter. The request requires no credentials. Successful exploitation causes the web server process to crash, denying administrative access and disrupting wireless guest network services until the device restarts or is reset.
No public exploit code or proof-of-concept has been released. Refer to the GitHub CVE Report for additional technical context.
Detection Methods for CVE-2025-70251
Indicators of Compromise
- Unexpected reboots or httpd process crashes on DIR-513 devices
- HTTP POST requests to /goform/formWlanGuestSetup containing abnormally long webPage parameter values
- Loss of management interface availability followed by automatic device recovery
- Inbound HTTP traffic to the router management interface from untrusted networks
Detection Strategies
- Inspect HTTP request bodies destined for the router for webPage parameters exceeding expected length thresholds (for example, more than 256 bytes)
- Alert on repeated HTTP 5xx responses or connection resets from the DIR-513 management interface
- Correlate router availability gaps with inbound HTTP traffic to goform/ endpoints
Monitoring Recommendations
- Forward router syslog and network flow data to a centralized SIEM for analysis
- Baseline normal administrative access patterns and alert on anomalous external sources
- Monitor for scanning activity targeting /goform/formWlanGuestSetup across the perimeter
How to Mitigate CVE-2025-70251
Immediate Actions Required
- Restrict access to the DIR-513 web management interface to trusted internal hosts only
- Disable remote management over the WAN if it is enabled
- Place the device behind a firewall that blocks unsolicited HTTP traffic to the router
- Plan replacement of the DIR-513 with a currently supported router model
Patch Information
No vendor patch is referenced in the NVD record for CVE-2025-70251. The D-Link DIR-513 is a legacy product. Consult the D-Link Security Bulletin for the latest guidance and any retirement or replacement notices. Where no firmware update is available, device replacement is the durable remediation.
Workarounds
- Block external access to TCP/80 and TCP/443 on the router from untrusted networks
- Segment the router management plane onto a dedicated VLAN with restricted ACLs
- Disable the guest wireless configuration feature if it is not in use
- Replace end-of-life D-Link DIR-513 hardware with a supported, actively maintained router
# Example firewall rule restricting router management to a trusted subnet
iptables -A INPUT -p tcp --dport 80 -s 192.0.2.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -s 192.0.2.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
