Alert! Unpatched critical Atlassian Confluence Zero-Day RCE flaw actively exploited

Atlassian warned of an actively exploited critical unpatched remote code execution flaw (CVE-2022-26134) in Confluence Server and Data Center products.

Atlassian is warning of a critical unpatched remote code execution vulnerability affecting all Confluence Server and Data Center supported versions, tracked as CVE-2022-26134, that is being actively exploited in attacks in the wild.

“Atlassian has been made aware of current active exploitation of a critical severity unauthenticated remote code execution vulnerability in Confluence Data Center and Server. Further details about the vulnerability are being withheld until a fix is available.” reads the advisory published by the company.

The issue was reported by security firm Volexity, the company announced the availability of the security fixes for supported versions of Confluence within 24 hours (estimated time, by EOD June 3 PDT).

Waiting for the fixes, Atlassian urges customers to restrict Confluence Server and Data Center instances from the internet or consider disabling Confluence Server and Data Center instances.

Volexity researchers discovered the issue as part of an investigation into an attack that took over the Memorial Day weekend.

The attackers targeted two Internet-facing web servers that were running Atlassian Confluence Server software. Volexity determined that threat actors launched an exploit to achieve remote code execution, they triggered a zero-day vulnerability that impacted fully up-to-date versions of Confluence Server.

“After successfully exploiting the Confluence Server systems, the attacker immediately deployed an in-memory copy of the BEHINDER implant. This is an ever-popular web server implant with source code available on GitHub. BEHINDER provides very powerful capabilities to attackers, including memory-only webshells and built-in support for interaction with Meterpreter and Cobalt Strike. As previously noted, this method of deployment has significant advantages by not writing files to disk. At the same time, it does not allow persistence, which means a reboot or service restart will wipe it out.” reads the analysis published by Volexity. “Once BEHINDER was deployed, the attacker used the in-memory webshell to deploy two additional webshells to disk: CHINA CHOPPER and a custom file upload shell.”

This isn’t the first time that flaws in Atlassian Confluence are exploited in attacks in the wild.

In September 2021, Trend Micro researchers spotted crypto-mining campaigns that were actively exploiting a recently disclosed critical remote code execution vulnerability in Atlassian Confluence deployments across Windows and Linux.

At the end of August 2021, Atlassian released security patches to address the critical CVE-2021-26084 flaw that affects the Confluence enterprise collaboration product.

The flaw is an OGNL injection issue that can be exploited by an authenticated attacker to execute arbitrary code on affected Confluence Server and Data Center instances.

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Pierluigi Paganini

(SecurityAffairs – hacking, Atlassian)

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