External risk intelligence

TOTOLINK A3100R Command Injection Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2021-44620

The affected product is a consumer router which provides network gateway services. Administrative interfaces on such devices are frequently exposed to the internet or are reachable by design to facilitate remote management, making the vulnerable endpoint public-facing in typical deployment scenarios.

Command Injection

Totolink A3100r Firmware

4.1.2cu.5050_b20200504 and earlier

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 command injection vulnerability has been identified in TOTOLINK routers, allowing unauthenticated remote attackers to execute arbitrary code. This could enable attackers to compromise the device and potentially impact network operations. The main concern is confirming relevance and exposure.

Attackers can run unauthorized commands on routers.
Routers are critical for network access and security.
Confirm if our network uses affected devices.

Attack Path

How an attacker could exploit the issue

An attacker could reach the vulnerability by accessing the administrative interface of the router, as the `adm/ntm.asp` page is exposed to the network. By manipulating the `hosTime` parameter, an attacker could inject arbitrary commands, potentially leading to complete system compromise.

No authentication required for access.
Triggered via a network-exposed administrative interface.
Leads to remote command execution.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could allow an unauthenticated attacker to execute arbitrary commands on the device when supported by the advisory. This could affect the device's operation and network services.

Device command execution.
Network access to vulnerable parameter.
Compromise of device network functions.

Operational Fix

Recommended remediation, mitigation, and detection steps

This critical command injection vulnerability in TOTOLINK routers requires a coordinated response. Typically, infrastructure or platform teams managing network devices would be responsible for identifying and assessing the risk of these devices. The first step is to locate all instances of the affected router model, determine their exposure (internal vs. external), and confirm business criticality to prioritize remediation efforts, engaging with the vendor as needed.

Infrastructure and platform teams own the issue.
Verify router reachability and business criticality.
Plan vendor-assisted remediation or replacement.

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 wireless router designed to provide home and small office network gateway services. These devices act as the central connectivity point for local networks, managing traffic flow between connected computers, mobile devices, and the internet.

What does command injection mean for CVE-2021-44620?

This vulnerability is classified as CWE-77, or Improper Neutralization of Special Elements used in an OS Command. In simple terms, it means the router's software fails to properly filter input. An attacker can use this flaw to 'inject' and run their own malicious operating system commands directly on the router, overriding its intended functions.

How is the vulnerability triggered?

The flaw is triggered by sending specially crafted input to the 'hosTime' parameter within the router's 'adm/ntm.asp' administrative page. It is important to note that the vulnerability is not triggered by standard web browsing traffic; the attacker must specifically target this administrative interface to execute the unauthorized commands.

Is my device at risk based on Halo Surface Signal?

According to Halo Surface Signal, this vulnerability is particularly relevant because the affected component is a gateway device. Administrative interfaces on routers like the A3100R are frequently reachable over the network by design, meaning if your router's management page is accessible from the internet, the device is considered public-facing and at higher risk.

What should I do if I use this router?

Begin by creating an inventory of all TOTOLINK A3100R devices in your environment to understand where they are deployed. Once identified, determine if they are exposed to the internet or restricted to internal traffic. Prioritize securing these devices by checking the vendor's official support resources for available firmware updates or guidance on limiting administrative access.

References

www.totolink.net/home/menu/newstpl/menu_newstpl/products/id/170.html

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.