Totolink X2000R Router Has Critical Stack Buffer Overflow in DHCP DNS Setup

The Totolink X2000R router contains a critical security flaw that allows remote attackers to execute arbitrary code on the device. This vulnerability stems from multiple stack-based buffer overflows within the boa formIpv6Setup dhcp_dns functionality. The issue concerns the dhcp_dns1 parameter processing logic. The flaw is rated 9.1 on the CVSS scale, indicating a high severity risk for any environment using this specific firmware version.

Root cause

The underlying technical issue is a CWE-121 stack-based buffer overflow. The vulnerability exists in the boa formIpv6Setup dhcp_dns functionality of the X2000R. Multiple exploitable stack-based buffer overflow vulnerabilities are present in this component. The specific parameter involved is dhcp_dns1. The source material identifies the weakness as CWE-121 but does not provide further technical details on the specific validation failure or memory corruption mechanism beyond the classification.

Attack path

Exploiting this vulnerability requires an attacker to first gain authenticated access to the router. Once logged in, the attacker sends a specially crafted HTTP request to trigger the vulnerabilities. The request targets the dhcp_dns1 parameter. Because the flaw allows arbitrary code execution, a successful exploit leads to arbitrary code execution on the device. The source material states that an attacker can make an authenticated HTTP request to trigger these vulnerabilities.

Affected versions

• TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327

Mitigation

• No patch or firmware update has been confirmed by the vendor for this vulnerability.
• Restrict access to the router's web management interface to trusted internal networks only.
• Disable remote administration features to prevent external attackers from reaching the login page.
• Use strong, unique credentials for the router's administrative account to raise the barrier for initial authentication.

Signals worth monitoring

Security operations teams should monitor web server logs for unusual HTTP POST requests targeting the formIpv6Setup endpoint. Look for requests containing abnormally large payloads in the dhcp_dns1 parameter, which may indicate an attempt to trigger a buffer overflow. Alert on successful authentication events followed immediately by configuration changes to DHCP or DNS settings. Check for unexpected outbound connections from the router, which could signal that an attacker has executed code and established a command-and-control channel. Review firewall logs for denied access attempts to the router's management port.

What to do and how to stay safe

• Audit your router's firmware version to determine if you are running the affected build.

Step-by-step guide: Attack Surface Management: 6 Common Misreadings and Correct Views

General security guidance from the NetSec Observer newsroom. It is not confirmed advice from the organisations named in this story.