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Dell laptops and computers vulnerable to remote hijacks

May 1, 2019

Another security flaw in a vendor’s bloatware apps puts users at risk.

A vulnerability in the Dell SupportAssist utility exposes Dell laptops and personal computers to a remote attack that can allow hackers to execute code with admin privileges on devices using an older version of this tool and take over users’ systems.

Dell has released a patch for this security flaw on April 23; however, many users are likely to remain vulnerable unless they’ve already updated the tool –which is used for debugging, diagnostics, and Dell drivers auto-updates.

The number of impacted users is believed to be very high, as the SupportAssist tool is one of the apps that Dell will pre-install on all Dell laptops and computers the company ships with a running Windows OS (systems sold without an OS are not impacted).

CVE-2019-3719

According to Bill Demirkapi, a 17-year-old security researcher from the US, the Dell SupportAssist app is vulnerable to a “remote code execution” vulnerability that under certain circumstances can allow attackers an easy way to hijack Dell systems.

The attack relies on luring users on a malicious web page, where JavaScript code can trick the Dell SupportAssist tool into downloading and running files from an attacker-controlled location.

Because the Dell SupportAssist tool runs as admin, attackers will have full access to targeted systems, if they manage to get themselves in the proper position to execute this attack.

ATTACK REQUIRES LAN/ROUTER COMPROMISE

“The attacker needs to be on the victim’s network in order to perform an ARP Spoofing Attack and a DNS Spoofing Attack on the victim’s machine in order to achieve remote code execution,” Demirkapi told ZDNet today in an email conversation.

This might sound hard, but it isn’t as complicated as it appears.

Two scenarios in which the attack could work include public WiFi networks or large enterprise networks where there’s at least one compromised machine that can be used to launch the ARP and DNS attacks against adjacent Dell systems running the SupportAssist tool.

Another plausible scenario is in situations where hackers have compromised the users’ local WiFi router, and are in a position to alter DNS traffic directly on the router.

As we’ve seen in the past few months, hacking routers to hijack DNS traffic isn’t a sophisticated attack anymore and is happening more and more often, mainly due to the sad state of router security.

ATTACK REQUIRES NO USER INTERACTION

Furthermore, the attack requires no user interaction except tricking users on accessing a malicious page, and the malicious JavaScript code that drives the attack can also be hidden inside ads (iframes) on legitimate sites, if ever necessary.

As Demirkapi explained to ZDNet, the iframe will point to a subdomain of dell.com, and then a DNS spoofing attack performed from an attacker-controlled machine/router will return an incorrect IP address for the dell.com domain, allowing the attacker to control what files are sent and executed by the SupportAssist tool.

The good news is that Dell took the researcher’s report seriously and has worked for the past months to patch CVE-2019-3719, a task that concluded last week with the release of SupportAssist v3.2.0.90, which Dell users are now advised to install.

Proof of concept to reproduce an attack is available on GitHub, and Demirkapi also published a demo video showing how easily an attack can lead to a full device compromise. Demirkapi’s vulnerability report, for additional technical details, is available on the young researcher’s blog.

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