External risk intelligence

Totolink A3100R Command Injection Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2021-46007

The affected product is a router/gateway device. Such consumer networking equipment is typically deployed as the internet edge gateway, making its management interface or web-based administrative services directly exposed to the public internet by design.

OS Command Injection

Totolink Ar3100r Firmware

5.9c.4577

Halo Surface Signal: 5 out of 5 — more likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A vulnerability in specific Totolink router firmware allows attackers to inject commands remotely, potentially enabling unauthorized control or access to network functions. The main concern is confirming relevance and exposure.

Remote command injection flaw in router firmware.
Potential for unauthorized network access or control.
Confirm exposure and relevance to our infrastructure.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by sending a specially crafted request to the router's web interface, which is exposed to the internet. The router's backend processes a "ping" command without properly sanitizing user input, allowing the attacker to inject malicious operating system commands. Successful exploitation could lead to a complete compromise of the device.

No authentication or user interaction needed.
Triggered by sending malicious input to the router.
Leads to operating system command injection.

Live Threat

Current exploitation, exposure, and threat context

The vulnerability allows for the execution of arbitrary operating system commands when the input field for the "ping" function does not properly filter special characters. This could enable an attacker to compromise the affected device.

System commands could be injected.
Attacker sends specially crafted network requests.
Device compromise and unauthorized access.

Operational Fix

Recommended remediation, mitigation, and detection steps

The "totolink a3100r_firmware" device, often deployed as an internet gateway, presents a critical command injection vulnerability. Infrastructure or network security teams should prioritize identifying all instances of this device, assessing their internet reachability and business criticality, and confirming the accountable owner for remediation. Planning should then focus on risk-based updates or temporary mitigation strategies.

Network or Infrastructure owners to address.
Verify internet-facing instances first.
Plan and coordinate remediation activities.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is the Totolink A3100R?

The Totolink A3100R is a consumer-grade router or gateway device used to manage network traffic. These devices typically function as an internet edge gateway, providing connectivity for home or small office networks by bridging the local network to an internet service provider.

What does CVE-2021-46007 mean?

This CVE refers to a vulnerability known as OS Command Injection (CWE-78). It happens when software fails to clean user-supplied input before passing it to a system command. In this case, the router's ping function does not filter special characters, allowing an attacker to insert and execute their own unauthorized operating system commands on the device.

How is the command injection triggered?

The flaw is triggered by sending a specially crafted request containing malicious input to the router's web interface. It does not require the attacker to have an existing account or password, nor does it require any interaction from a legitimate user. Simple, standard network requests are sufficient to initiate the vulnerability.

Is my device at risk if it is not internet-facing?

Halo Surface Signal indicates that because this product is an edge gateway, it is often exposed to the public internet by design, which significantly increases risk. If your device is located strictly behind another firewall or restricted to internal management only, the external attack surface is reduced, but the underlying firmware flaw remains.

What should I do if I run this firmware?

First, identify all instances of the affected firmware version within your environment. Prioritize those that are directly accessible from the internet, as these are the most accessible to potential attackers. Once identified, coordinate with the infrastructure owners to plan and apply necessary firmware updates or implement temporary mitigations to secure the device.

References

hackmd.io/t_nRWxS2Q2O7GV2E5BhQMg

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.