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Wednesday, 21 April 2021 10:32

FireEye finds SonicWall zero-days being exploited in the wild

FireEye finds SonicWall zero-days being exploited in the wild Image by neo tam from Pixabay

Three zero-day vulnerabilities in SonicWall's Email Security product that were being exploited in the wild have been reported by American security firm FireEye's Mandiant Managed Defence unit.

The company has released hotfixes for Windows users and and also for hardware and ESXi virtual appliance users.

In a detailed blog post, researchers Josh Fleischer, Chris DiGiamo and Alex Pennino said the three flaws were run in conjunction to obtain admin access and execute code on a SonicWall ES device.

The attacker(s), who appeared to have complete knowledge of the device, used these vulnerabilities to install a backdoor, gain access to files and emails and move laterally within the target organisation's network.

The three vulnerabilities were listed as:

  • CVE-2021-20021 (CVSS score 9.4) Unauthorised administrative account creation;
  • CVE-2021-20022 (CVSS score 6.7) Post-authentication arbitrary file upload; and
  • CVE-2021-20023 (CVSS score 6.7) Post-authentication arbitrary file read.

The trio said the SonicWall Hosted Email Security product was automatically updated and the hotfixes would be superseded by the upcoming SonicWall ES 10.0.10 release.

Fleischer, DiGiamo and Pennino wrote that they had found post-exploitation Web activity on an Internet-connected system in a customer's premises. This was isolated and examined for evidence to find out how the compromise had been effected.


SonicWall Email Security ecosystem overview. Courtesy SonicWall

"The system was quickly identified as a SonicWall Email Security application running on a standard Windows Server 2012 installation," they said. "The adversary-installed Web shell was being served through the HTTPS-enabled Apache Tomcat Web server bundled with SonicWall ES.

"Due to the Web shell being served in the application’s bundled Web server, we immediately suspected the compromise was associated with the SonicWall ES application itself."

Later, they found logs that showed the attacker(s) had tried to destroy evidence of the intrusion. However, other logs provided the evidence which the researchers sought.

The trio said this activity was being tracked as UNC2682. "An UNC group is a cluster of related cyber-intrusion activity, which includes observable artifacts such as adversary infrastructure, tools, and tradecraft, that we are not yet ready to give a classification such as APT [advanced persistent threat] or FIN [a type of port scan]," they said.

Two of the three flaws were notified to SonicWall on 26 March, acknowledged three days later, and fixes made available on 9 April. The third vulnerability was notified to SonicWall on 9 April and a patch was released on 19 April.

SonicWall has released a statement about the vulnerabilities on its website.

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Sam Varghese

Sam Varghese has been writing for iTWire since 2006, a year after the site came into existence. For nearly a decade thereafter, he wrote mostly about free and open source software, based on his own use of this genre of software. Since May 2016, he has been writing across many areas of technology. He has been a journalist for nearly 40 years in India (Indian Express and Deccan Herald), the UAE (Khaleej Times) and Australia (Daily Commercial News (now defunct) and The Age). His personal blog is titled Irregular Expression.

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