How do I check whether I am affected by CVE-2026-42021?

In the router admin UI (System status / firmware info) read the firmware version; build TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327 is the one confirmed vulnerable. Other builds are untested, not known safe. Also check whether the admin web interface (boa, port 80) is reachable from WAN.

What is the fix for CVE-2026-42021?

No fixed firmware published that I could find (unknown; check https://www.totolink.net/home/menu/newstpl/menu_newstpl/products/id/242.html). Mitigation: disable remote/WAN web administration, restrict admin UI to a trusted LAN, change default admin password, since exploit needs a valid login.

Who is not affected by CVE-2026-42021?

Not affected if: auth-required, other-router-models.

Live › vulnerability › CVE-2026-42021

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critical9.1Infrastructure

TOTOLINK X2000R router: IPv6 setup overflow lets attackers run code

The web management interface (boa) on the TOTOLINK X2000R router has stack buffer overflows in its IPv6 static network configuration handler, triggered through the static_dns1 parameter. An attacker who holds a valid login can send a crafted HTTP request to run arbitrary code on the router.

Summary written from the sources below. Check the originals before acting.

CVSS 3.x

9.1

critical

scored by [email protected]

known so far5 of 6

missing: exploitation

First public: Oct 20, 2026 UTC
Last modified: Oct 23, 2026
Status: open
Known exploitation: None reported
Public exploit: None on GitHub
EPSS: not scored

First seen by InfraStack 2026-10-23 21:57 UTC. All times on this page are UTC.

Why it is critical, and not just CVSS

Likelihood → · Impact ↓

critical

high

medium

high

medium

low

medium

low

Exploited: No reports yet.
Needs login: Yes.
Needs a special setup: Not known from the sources.
Reachable from: network.
Worst case: Attacker runs code on the router as root and controls network traffic.
CVSS said: 9.1. The facts above say medium; we keep the sources' critical until an analyst looks.

Who is affected

1 product

Know the next one before it finds you.

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Live › vulnerability › CVE-2026-42021

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critical9.1Infrastructure

TOTOLINK X2000R router: IPv6 setup overflow lets attackers run code

Summary written from the sources below. Check the originals before acting.

CVSS 3.x

9.1

critical

scored by [email protected]

known so far5 of 6

missing: exploitation

First public: Oct 20, 2026 UTC
Last modified: Oct 23, 2026
Status: open
Known exploitation: None reported
Public exploit: None on GitHub
EPSS: not scored

First seen by InfraStack 2026-10-23 21:57 UTC. All times on this page are UTC.

Why it is critical, and not just CVSS

Likelihood → · Impact ↓

critical

high

medium

high

medium

low

medium

low

Exploited: No reports yet.
Needs login: Yes.
Needs a special setup: Not known from the sources.
Reachable from: network.
Worst case: Attacker runs code on the router as root and controls network traffic.
CVSS said: 9.1. The facts above say medium; we keep the sources' critical until an analyst looks.

Who is affected

1 product

Know the next one before it finds you.

Add to Slack

TOTOLINK X2000R router: IPv6 setup overflow lets attackers run code

Why it is critical, and not just CVSS

Who is affected

Know the next one before it finds you.

TOTOLINK X2000R router: IPv6 setup overflow lets attackers run code

Why it is critical, and not just CVSS

Who is affected

Know the next one before it finds you.

How to check

The fix

Who had it, and when

What the sources say, verbatim

Sources