Sitecore XP RCE flaw is being actively exploited, ACSC warns

The Australian Cyber Security Center (ACSC) has cautioned organizations that hackers are actively exploiting a remote code execution flaw in the Sitecore Experience Platform (Sitecore XP).

Successful exploitation of the vulnerability (CVE-2021-42237) results in remote code execution that “could allow an internet-based actor to install malware/ or webshells and perform other actions”, ACSC said in a statement.

“The ACSC is aware of active exploitation of this vulnerability in Australia,” it added.

Sitecore XP is a content management system (CMS) that combines customer data, analytics, artificial intelligence (AI), and marketing automation capabilities. This CMS is used heavily by enterprises, including many of the companies within the Fortune 500. The company rolled out a patch for the flaw in October.

“The vulnerability is related to a remote code execution vulnerability through insecure deserialization in the Report.ashx file," Sitecore said in a security advisory. "This file was used to drive the Executive Insight Dashboard (of Silverlight report) that was deprecated in 8.0 Initial Release."

The firm added that the vulnerability applies to all Sitecore systems running affected versions, including single-instance and multi-instance environments, Managed Cloud environments, and all Sitecore server roles (content delivery, content editing, reporting, processing, etc.), which are exposed to the internet.

According to Mitre’s CVE website on the flaw, Sitecore XP 7.5 Initial Release to Sitecore XP 8.2 Update-7 is “vulnerable to an insecure deserialization attack where it is possible to achieve remote command execution on the machine. No authentication or special configuration is required to exploit this vulnerability.”

The flaw was first picked up by security researchers at Assetnote. Shubham Shah, co-founder, and CTO of Assetnote, said that while investigating the Sitecore product and its source code, his team found that the code does not require any authentication.

Shah added to remediate this vulnerability, admins can remove the Report.ashx file from /sitecore/shell/ClientBin/Reporting/. He said that in performing offensive security source code analysis his team often discovers there are critical vulnerabilities in enterprise software that are incredibly easy to exploit.

“The apps that we have been auditing are complex, however, the vulnerabilities are quite simple. With a concerted effort in taking apart these enterprise apps, we are able to discover critical vulnerabilities, after understanding the attack surface,” he said.

Sitecore has advised users to upgrade to version 9.0.0 or higher which protects against the vulnerability.