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TOTOLINK X2000R EUVDEUVD-2026-105344

| CVE-2026-42019 CRITICAL
Stack-based Buffer Overflow (CWE-121)
2026-10-20 talos GHSA-6934-8h2c-7627
9.1
CVSS 3.1 · Vendor: talos
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Obtain authenticated admin access to router
  2. Delivery
    Craft HTTP request with oversized pppoe_dns1 value
  3. Exploit
    Overflow stack buffer in boa formIpv6Setup handler
  4. Execution
    Execute arbitrary code on device
  5. Impact
    Gain control of router

Vulnerability Assessment

Weakness
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Stack buffer bounds checking
MITRE ATT&CK

1 technique across 1 tactic: Execution

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Exploitation Conditions

Exploitation requires an authenticated HTTP request to the boa web server's formIpv6Setup PPPoE configuration endpoint, specifically supplying an overlong value in the pppoe_dns1 parameter; the device must be running the affected firmware TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327. The key limiting factor is that valid management-interface authentication (PR:H) is mandatory - the attacker must already possess admin credentials or obtain them (default/weak passwords, credential reuse, or a chained auth bypass). Network reachability to the router's HTTP management interface is also required, which in default deployments is typically LAN-side only.

Impact

The input provides a CVSS 3.1 vector (AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H, 9.1 Critical) indicating a network-reachable, low-complexity flaw that yields full confidentiality, integrity, and availability loss - consistent with arbitrary code execution on an embedded web server (boa). The critical limiting signal is PR:H: per the CVSS vector and the description ('authenticated HTTP request'), exploitation requires valid authenticated access to the device management interface, which substantially lowers real-world risk versus a pre-auth flaw. No EPSS score, CISA KEV listing, or POC indicator is present in the input, so there is no evidence of active or likely-imminent exploitation; per precision rules this is 'no public exploit identified at time of analysis.' The S:C (scope changed) claim is debatable for a monolithic embedded router where the web server typically runs as root in a single privilege domain - verify scope framing with the vendor/Talos report. Net assessment: a genuinely severe code-execution bug, but the authentication requirement makes it a post-compromise or credentialed-attacker concern (e.g., default/weak credentials, chained with an auth bypass) rather than a mass-exploitation priority absent exploitation telemetry.

Exploit ScenarioDerived

An attacker who already holds valid management credentials (or who reached the admin panel via default/reused credentials) sends a specially crafted HTTP request to the formIpv6Setup PPPoE handler with an oversized pppoe_dns1 value, overflowing a stack buffer in the boa web server and executing arbitrary code on the router. No public POC or exploit code is identified in the provided data.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.
No patch listed yet 0.7% exploitation probability (EPSS)

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AnalysisAIv1 – Oct 20, 2026

Arbitrary code execution in TOTOLINK X2000R firmware (TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327) is possible through a stack-based buffer overflow in the boa web server's formIpv6Setup PPPoE handler when the pppoe_dns1 parameter receives an overlong value. The attack requires an authenticated HTTP request with valid management credentials (CVSS PR:H) and network reachability to the router's management interface, which is typically LAN-side. No public exploit was identified at time of analysis; Talos rates the issue 9.1 critical under a scope-changed vector, while the independent assessment scopes the impact to the device (S:U) and still considers it high severity.

RemediationAI

No vendor-released patch was identified at time of analysis; check the Talos advisory TALOS-2026-2394 (https://talosintelligence.com/vulnerability_reports/TALOS-2026-2394) and TOTOLINK support for updated X2000R firmware and apply it when available. Until then, restrict access to the router's HTTP management interface to trusted LAN/VLAN segments or a VPN/allowlisted admin host and disable WAN-side remote management where possible; the trade-off is loss of convenient remote administration. Replace default or weak admin credentials with strong unique passwords and rotate them, which raises the PR:H bar but does not remove the overflow. If the IPv6/PPPoE setup feature is not needed, disable it or restrict access to that configuration page; this reduces exposure but may prevent legitimate WAN configuration changes. Deploy monitoring or IDS rules for oversized pppoe_dns1 values or abnormal requests to formIpv6Setup as a detection control, noting that detection does not prevent exploitation.

Affected VersionsENISA

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

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Technical ContextAI · show details

The flaw is CWE-121 stack-based buffer overflow in the boa embedded HTTP server used by TOTOLINK X2000R routers. The formIpv6Setup functionality handles IPv6/PPPoE configuration, and the pppoe_dns1 parameter is copied into a fixed-size stack buffer without sufficient bounds checking; a crafted HTTP request can overwrite stack memory and redirect execution, yielding arbitrary code execution in the context of the boa service. The affected build is TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327; the supplied CPE is broad (totolink:totolink:*), so exact build validation is important. The assessed vector is AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H, meaning the attacker must already hold administrative credentials and reach the management interface; it is not an unauthenticated pre-auth overflow. Talos's published 9.1 score uses S:C, reflecting potential impact beyond the vulnerable component, but the independent assessment treats scope as unchanged.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (talos) PRIMARY 9.1 CRITICAL
AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
vuln.today AI 7.2 HIGH

Network-reachable, low-complexity overflow requiring authenticated admin access (PR:H); scope assessed Unchanged since the boa server already runs with full device privileges, yielding full C/I/A impact.

3.1 AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
4.0 AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (talos).

CVSS VectorVendor: talos

Attack Vector
Network
Attack Complexity
Low
Privileges Required
High
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

DescriptionCVE.org

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_dns1 parameter.

Executive ViewAI

Why It Matters

The TOTOLINK X2000R router firmware (TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327) contains a critical arbitrary code execution vulnerability in its web management interface. An attacker who already holds valid high-privilege management credentials and can reach the management interface-typically from the LAN side-could exploit a stack-based buffer overflow in the PPPoE handler to run code on the device. Because these routers may act as network gateways for small offices or remote sites, a compromise could undermine network integrity and provide a foothold for further intrusion, making inventory and mitigation a priority despite the authenticated access requirement and no public exploit identified at time of analysis.

Business Impact: High
Compensating Controls

No vendor-released patch identified at time of analysis; restrict management interface access to trusted LAN only, enforce strong unique administrative credentials, disable WAN-side and remote management, segment affected routers, and monitor for unauthorized configuration changes.

Threat Intelligence Overview

EPSS Score
0.7%
Top 46% exploitable
Prevalence
Low
specific TOTOLINK consumer/SOHO router model, limited deployment footprint
Data Quality
4 sources
Confidence: Medium

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity CRITICAL
CISA KEV No
Public POC No
EPSS 0.7%
Patch available No
Active threat No
Deciding rule
CRITICAL severity
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
No
Human Impact
High

Priority Score

47
Low Medium High Critical
KEV: 0
EPSS: +1
CVSS: +46
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.

A stack-based buffer overflow occurs when a program writes more data to a buffer located on the stack than it was allocated to hold.

Remote Code Execution represents the critical moment when an attacker successfully runs arbitrary code on a target system without physical access.

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