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CriticalVulnerabilityCVE-2026-42021updated 25 Oct 2026, 15:22 UTC

TOTOLINK X2000R router can be taken over via crafted IPv6 settings request

A specially crafted request to the router's web settings page can overflow memory and let an attacker run their own code on the device. A logged-in user (or attacker with login access) is needed to send it.

Official, 2 sources
SeverityCriticalCVSS 9.1 of 10
Being exploited?UnclearNo reports either way yet
Fix available?UnclearNo fixed version published in the sources yet
How sure is this?Official, 2 sourcesBacked by an official source

How the attack works simplified

  1. 1Attacker logs inNeeds authenticated access to the web interface
  2. 2Crafted HTTP requestSent to the IPv6 setup page
  3. 3Oversized DNS valuestatic_dns1 parameter overflows the buffer
  4. 4Code runs on routerStack overflow enables arbitrary code execution
  5. ResultAttacker controls the router

What happened

Stack-based buffer overflows in the boa formIpv6Setup static network configuration handler, triggered via the static_dns1 parameter, allow arbitrary code execution on the TOTOLINK X2000R firmware TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327.

Why it is dangerous: Successful exploitation gives an attacker control of the router, which can expose the home or office network, intercept or redirect traffic, and pivot to other devices.

Are you affected?

You are affected if you run TOTOLINK X2000R with firmware TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327 and its web management interface is reachable by untrusted users or the internet.

TOTOLINK X2000R, firmware TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327

What to do

  1. Check whether your router runs TOTOLINK X2000R firmware B20250421.1327 and update to a vendor-released fixed firmware as soon as one is available
  2. Disable remote web management and do not expose the router's admin page to the internet
  3. Restrict access to the admin page to trusted devices and change the default admin password

Timeline

  1. 20 Oct 2026, 21:17 UTC
    Publicly disclosed
  2. 20 Oct 2026, 21:17 UTC
    Reported by NVD · NVD
  3. 25 Oct 2026, 15:22 UTC
    GitHub Advisory reported on it · GitHub Advisory

Sources 2 reports, oldest first

Official vendor, government CERT or advisory database

Technical details

ID
CVE-2026-42021 · GHSA-9hw7-42mj-hjfc
CVSS
9.1 / 10
EPSS
0.5% chance of exploitation within 30 days
Disclosed
20 Oct 2026, 21:17 UTC
On Zero Radar
before the radar started
Last change
25 Oct 2026, 15:22 UTC

The plain-language parts and the attack diagram were written by an AI model (anthropic/claude-haiku-5.5) from the sources above. Facts like versions, exploitation and dates come from the sources themselves. How Zero Radar works

TOTOLINK X2000R router can be taken over via crafted IPv6 settings request · Zero Radar