External risk intelligence

TP-Link Archer A7 Command Injection Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2021-42232

This vulnerability affects a consumer router, a device commonly deployed at the network edge to provide internet connectivity. As a network gateway and routing appliance, such devices are frequently exposed directly to the public internet to facilitate wide area network communications.

OS Command Injection

Tp Link Archer A7 Firmware

210519

Halo Surface Signal: 4 out of 5 — 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 TP-Link Archer A7 routers. This flaw allows attackers to execute arbitrary commands on the affected devices, potentially compromising network security. The main concern is confirming the relevance and exposure of this vulnerability within our environment.

Router flaw allows unauthorized command execution.
Pervasive consumer technology is often a target.
Assess impact on our network edge devices.

Attack Path

How an attacker could exploit the issue

An attacker can exploit this vulnerability by sending specially crafted data packets over the network to the router. The vulnerable `tddp` program within the router improperly handles parts of these incoming data packets, incorporating them directly into system commands. This allows an attacker to inject and execute arbitrary commands, potentially leading to full control of the affected device.

Accessible via the network.
Exploited by sending crafted data packets.
Allows arbitrary command execution.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could allow an attacker to execute arbitrary commands on the router by sending a specially crafted data packet. This could affect the router's functionality and potentially compromise the network it manages.

Router system commands.
Via crafted network data packet.
Unauthorized command execution.

Operational Fix

Recommended remediation, mitigation, and detection steps

The command injection vulnerability in TP-Link Archer A7 firmware's `tddp` program necessitates a coordinated response. Given that this is a consumer router, the primary responsibility likely falls to the asset owner or the team managing the network edge infrastructure. The initial crucial step is to identify all instances of this affected device, determine their exposure to the internet, and confirm their business criticality before planning any remediation or mitigation.

Asset owners should assume responsibility for this issue.
Verify internet-facing router presence and criticality.
Plan remediation or risk reduction strategies.

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 TP-Link Archer A7?

The TP-Link Archer A7 is a consumer-grade wireless router. It acts as a gateway for home or small office networks, managing traffic between the local network and the internet while providing Wi-Fi connectivity to various devices.

What does command injection mean for CVE-2021-42232?

This vulnerability, classified as CWE-78, occurs when the router's software processes network data incorrectly. Because the system treats parts of an incoming data packet as an executable command, an attacker can trick the router into running unintended instructions, effectively gaining control over the device.

How can an attacker trigger this vulnerability?

An attacker triggers this flaw by sending a specially crafted data packet to the router's tddp program. It is important to note that this is not triggered by normal user traffic or typical web browsing; it requires specific, malicious input designed to exploit how the device handles these data packets.

Is my Archer A7 at risk?

According to Halo Surface Signal, this vulnerability is significant because consumer routers often sit at the network edge, making them directly reachable from the public internet. If your device is configured to allow network-based access, it is considered exposed to this type of remote attack.

What should I do if I use this router?

Begin by verifying if you have the affected firmware version installed on your device. Once identified, check if the router is directly connected to the internet and assess its role in your network. Prioritize determining your update options to mitigate the command injection risk.

References

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.