Vulnerability in Linear eMerge Access Controllers Exploited in the Wild

03 February 2020

Vulnerability in Linear eMerge Access Controllers Exploited in the Wild

Hackers are actively targeting a vulnerability in Linear eMerge E3 access controllers to infect the devices with malware and abuse them to launch distributed denial-of-service (DDoS) attacks, SonicWall revealed over the weekend.

A Nortek Security and Control LLC product, the Linear eMerge E3 access controller is used in the commercial, industrial, banking, medical, retail, and hospitality sectors to manage user access to specific facilities or areas.

In April last year, Gjoko Krstic, a researcher at industrial cybersecurity firm Applied Risk, presented at SecurityWeek’s ICS Cyber Security Conference in Singapore information on vulnerabilities found in building management and access control systems from various vendors, including Nortek.

Out of more than 100 vulnerabilities Krstic found in the analyzed systems during a year-long investigation, 10 were impacting Nortek’s Linear eMerge E3 product, and six of them were considered critical.

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Now, nearly one year later, SonicWall says it is seeing tens of thousands of daily attempts to exploit one of the critical vulnerabilities Applied Risk discovered in the eMerge E3 access controllers.

Tracked as CVE-2019-7256, the flaw is a command injection vulnerability that results from the insufficient sanitization of user-supplied input to a PHP function. The issue can be exploited to achieve arbitrary command execution with root privileges.

“The application constructs an OS command using externally-influenced input from an upstream component, but incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component,” reads an advisory from Applied Risk.

As SonicWall explains, an adversary could exploit the vulnerability remotely without authentication, via a crafted HTTP request, and this is exactly the type of attack that is being observed in the wild right now.

Following the successful exploitation of the vulnerability, a shell command is executed to download malware and install it on the vulnerable system. The malware can then be leveraged to launch various types of DDoS attacks.

The issue affects Linear eMerge Elite/Essential firmware version 1.00-06, and over 2,300 potentially affected devices are exposed to the internet.

“Attackers seem to be actively targeting these devices as we see tens of thousands of hits every day, targeting over 100 countries with the most observed in U.S.,” SonicWall says.

Last year, Krstic told SecurityWeek that Nortek was the only manufacturer that refused communication with Applied Risk, while others resolved the reported issues. Nortek claimed at the time that the vulnerabilities had been addressed, but Applied Risk said it never actually got the chance to share vulnerability details with the vendor.