Threat Signal Report

Path Traversal Vulnerability in Arcadyan Firmware Putting Millions of IoT Devices at Risk

description-logo Description

FortiGuard Labs is aware of a report that a path traversal vulnerability (CVE-2021-20090) in Arcadyan firmware used in routers leads to an authentication bypass. Successfully exploiting the vulnerability allows the attacker to bypass authentication to access restricted pages and perform any action on the device without authentication. According to security vendor Tenable, the vulnerability in Arcadyan's firmware, "has existed for at least 10 years and has therefore found its way through the supply chain into at least 20 models across 17 different vendors." There also is a report that the vulnerability is being exploited in the wild in order to deploy Mirai malware.

When was the Vulnerability Disclosed?

The vulnerability was disclosed by security vendor Tenable on August 3rd, 2021.

How Serious of an Issue is This?

HIGH. According to Tenable, the vulnerability has existed for at least 10 years and has therefore found its way through the supply chain into at least 20 models across 17 different vendors". Also security vendor Juniper reported that the vulnerability is being exploited in the wild in order to deploy Mirai malware.

Many routers do not receive periodic security updates from their manufacturers and when they do they most often need to be applied manually.

What is the Vulnerability Exploited in this Attack in Order to Deliver Mirai malware?

The exploited vulnerability is a path traversal vulnerability (CVE-2021-20090), which allows unauthenticated users to access restricted pages and take control of the affected device. The vulnerability is in Arcadyan's router firmware that is used by various router manufactures.

Which Routers are Affected?

Tenable provided the following list of affected routers. Note that as Tenable stated the vulnerability has existed more than 10 years, there may be other affected routers." dir="ltr" style="font-size: 10pt; line-height: 1.1; margin: 1em 0px; padding: 0px; width: 813px; color: rgb(119, 119, 121); table-layout: fixed; font-family: Arial; border: none;" height="878" cellspacing="0" cellpadding="0" border="1">
VendorDeviceFound on version
ADBADSL wireless IAD router1.26S-R-3P
ArcadyanVRV95176.00.17 build04
ArcadyanVRV95181.01.00 build44
ASUSDSL-AC88U (Arc VRV9517)1.10.05 build502
ASUSDSL-AC87VG (Arc VRV9510)1.05.18 build305
ASUSDSL-AC31001.10.05 build503
ASUSDSL-AC68VG5.00.08 build272
BeelineSmart Box Flash1.00.13_beta4
British TelecomWE410443-SA1.02.12 build02
BuffaloBBR-4MG2.08 Release 0002
Deutsche TelekomSpeedport Smart 3010137.
KPNExperiaBox V10A (Arcadyan VRV9517)5.00.48 build453
O2HomeBox 64411.01.36
OrangeLiveBox Fibra (PRV3399)
SkinnySmart Modem (Arcadyan VRV9517)6.00.16 build01
SparkNZSmart Modem (Arcadyan VRV9517)6.00.17 build04
Telecom (Argentina)Arcadyan VRV9518VAC23-A-OS-AM1.01.00 build44
TelstraSmart Modem Gen 2 (LH1000)0.13.01r
TelusWiFi Hub (PRV65B444A-S-TS)v3.00.20
TelusNH20A1.00.10debug build06
VerizonFios G31002.0.0.6
VodafoneEasyBox 9044.16
VodafoneEasyBox 90330.05.714
VodafoneEasyBox 80220.02.226

What is Mirai Malware?

Mirai is a Linux malware that targets IoT devices to form a Mirai botnet which is typically used for large-scale DDoS attacks. Mirai's source code was made available in 2016 by a Hackforums user "Anna-senpai", named after a female character in Japanese novel "Shimoneta: A Boring World Where the Concept of Dirty Jokes Doesn't Exist", which prompted other attackers to develop and release subsequent variants.

FortiGuard Labs recently published a blog on Mirai malware and its variants. Please see a link to "The Ghosts of Mirai" in the Appendix.

Is the Patch Available for CVE-2021-20090?

Unconfirmed as the vulnerability needs to be fixed by each router manufactures.

What is the Status of Coverage?

Customers running the latest IPS definitions are protected by the following signature:


FortiGuard Labs provides the following AV coverage for the associated Miral malware, some of which are not directly related to the attack but came from the same IP involved in the CVE-2021-20090 attack:












All known network IOC's are blocked by the FortiGuard WebFiltering client.

Any Other Suggested Mitigation?

As a mitigation, FortiGuard Labs recommends to disable the remote (WAN-side) administration services on the affected router and disable the web interface on the WAN.



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