Pierluigi Paganini September 03, 2021

USCYBERCOM is urging organizations to patch a critical CVE-2021-26084 flaw in Atlassian Confluence Server and Data Center, ahead of the Labor Day weekend. 

US Cyber Command (USCYBERCOM) has issued an alert to warn US organizations to address Atlassian Confluence CVE-2021-26084 vulnerability immediately, ahead of the Labor Day weekend.

Government experts are aware of the ongoing mass exploitation of the CVE-2021-26084 flaw and believe it could rapidly accelerate.

Threat actors started exploiting the CVE-2021-26084 vulnerability in Atlassian’s Confluence enterprise collaboration product a few days after it was patched by the vendor. At the time of this writing, experts only observed threat actors exploiting the issue to deliver cryptocurrency miners, but attackers could start exploiting them to deliver other malware, including ransomware.

Last week, 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.

“An OGNL injection vulnerability exists that would allow an authenticated user, and in some instances unauthenticated user, to execute arbitrary code on a Confluence Server or Data Center instance. ” reads the advisory published by the company.

The issue was discovered by Benny Jacob (SnowyOwl) through the Atlassian public bug bounty program, the vulnerability received a CVSS score of 9.8.

Affected versions are:

• version < 6.13.23
• 6.14.0 ≤ version < 7.4.11
• 7.5.0 ≤ version < 7.11.5
• 7.12.0 ≤ version < 7.12.5

Researchers from Threat intelligence firm Bad Packets detected mass scanning and exploit activity targeting Atlassian Confluence servers vulnerable to the above RCE.

CISA also published a security advisory to urge admins to apply the Confluence security updates released on August 25, 2021by Atlassian.

“On August 25, 2021, Atlassian released security updates to address a remote code execution vulnerability (CVE-2021-26084) affecting Confluence Server and Data Center. Recently, CVE-2021-26084 has been detected in exploits in the wild. A remote attacker could exploit this vulnerability to take control of an affected system.” reads the CISA’s alert. “CISA urges users and administrators to review Atlassian Security Advisory 2021-08-25 and immediately apply the necessary updates.”

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Pierluigi Paganini

(SecurityAffairs – hacking, CISA)

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