---
id: "CVE-2026-42020"
kind: "vulnerability"
aliases: ["CVE-2026-42020"]
title: "Totolink X2000R router: stack overflow in IPv6 PPPoE setup lets attackers run code"
severity: "critical"
cvss: 9.1
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: [{"name": "Totolink X2000R firmware", "fixed": [], "affected": "TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327", "ecosystem": "firmware"}]
ecosystems: []
tags: ["infrastructure", "router", "self-hosted", "totolink", "x2000r"]
not_affected_if: ["auth-required", "remote-management-disabled"]
published_at: "2026-10-20T21:17:19+00:00"
first_seen_at: "2026-10-23T21:57:21+00:00"
updated_at: "2026-10-23T23:13:36+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-42020", "first_seen_at": "2026-10-23T21:57:21+00:00"}, {"source": "analyst", "url": null, "first_seen_at": "2026-10-23T23:13:36+00:00"}]
---

# Totolink X2000R router: stack overflow in IPv6 PPPoE setup lets attackers run code

Stack buffer overflows in the boa web server's formIpv6Setup PPPoE handler (pppoe_dns2 parameter) on Totolink X2000R firmware B20250421.1327 allow code execution via a crafted HTTP request. Requires admin login (CVSS 9.1, PR:H); no fix or public exploit known.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- firmware:Totolink X2000R firmware affected TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327 fixed ?

## How to check

In the router web UI (System/Status page) read the firmware version; affected if it is TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327. Also check whether the admin web interface (boa) is reachable from WAN.

## Fix

No fixed firmware published as of 2026-10-23 (unknown). Check TOTOLINK's download page for X2000R. Mitigate: disable WAN/remote management, restrict the admin UI to a trusted LAN, change the default admin password, and avoid IPv6 PPPoE setup from untrusted users.

## Timeline

- 2026-10-23T21:57:21+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-42020
- 2026-10-23T23:13:36+00:00 analyst — CVE.org record and VulDB read: only build TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327 listed; no vendor advisory, no fixed firmware, no public exploit, not in KEV, no social discussion checked.

## Documents

- [advisory] CVE Record: CVE-2026-42020 https://www.cve.org/CVERecord?id=CVE-2026-42020
- [mentions] VulDB: Totolink X2000R formIpv6Setup pppoe_dns2 buffer overflow https://vuldb.com/vuln/424068

## From the sources

Multiple stack-based buffer overflow vulnerabilities exist in the boa formIpv6Setup pppoe functionality of Totolink X2000R TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327. A specially crafted HTTP request can lead to arbitrary code execution. An attacker can make an authenticated HTTP request to trigger these vulnerabilities. This vulnerability concerns the pppoe_dns2 parameter.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_