Atlassian rolled out fixes for Confluence zero-day actively exploited in the wild

Atlassian has addressed on Friday an actively exploited critical remote code execution flaw (CVE-2022-26134) in Confluence Server and Data Center products.

Early this week, Atlassian warned 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).

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.”

The company on Friday released security fixes to address the CVE-2022-26134 critical security flaw.

According to Atlassian, the patches fixed the issue in the following versions of the software:

IoT search engine Censys has found around 9,325 services across 8,347 distinct hosts running some version of Atlassian Confluence.

“Of those services, most Confluence versions we identified were v7.13.0 (1,137 hosts), v7.13.2 (690 hosts), and v7.13.5 (429 hosts); and if the advisory is accurate, all of these versions are susceptible to this new attack.” reads the advisory published by Censys.

Most of the installs are located in the U.S., China, and Germany.

“It is clear that multiple threat groups and individual actors have the exploit and have been using it in different ways. Some are quite sloppy and others are a bit more stealth.”

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) added the flaw to its Known Exploited Vulnerabilities Catalog and ordered federal agencies to immediately block all internet traffic to and from the affected products and a flaw by June 6, 2022, 5 p.m. ET.

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Pierluigi Paganini

(SecurityAffairs – hacking, Atlassian)