Atlassian Confluence is under heavy attack

Cybersecurity researchers at the US Cyber Command (USCYBERCOM) have urged admins to immediately patch their on-premise Atlassian Confluence collaboration platform, which is at the receiving end of an ongoing attack.

USCYBERCOM put out a public notice on Twitter informing Atlassian users of an active large-scale exploitation campaign that it expects to accelerate.

“Please patch immediately if you haven’t already—this cannot wait until after the weekend,” USCYBERCOM wrote on Twitter.

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The flaw, tracked as CVE-2021-26084, enables threat actors to remotely execute arbitrary code on the popular workplace collaboration platform.

Ongoing campaign

Described as “an OGNL injection vulnerability,” the bug exists in the Atlassian Confluence Server and Confluence Data Center products, both of which are vulnerable to unauthenticated remote attackers.

With a high CVSS severity rating of 9.8 out of 10, the vulnerability was first reported on July 27, 2021. However, given its serious nature, Atlassian didn’t publish details about its exploitation mechanism, even after it had issued a patch last month on August 25, 2021.

Reportedly however, threat actors began exploiting the vulnerability soon after the patch was released. Threat intelligence firm Bad Packets first detected “mass scanning and exploit activity” against the vulnerability from hosts in Brazil, China, Hong Kong, Nepal, Romania, Russia and the US, before Atlassian updated its advisory warning users about the attack.

“This vulnerability is being actively exploited in the wild. Affected servers should be patched immediately,” said Atlassian.

The vulnerability affects Confluence Server and Data Center versions before version 6.13.23, from version 6.14.0 before 7.4.11, from version 7.5.0 before 7.11.6, and from version 7.12.0 before 7.12.5.