CISA Issues Alert Over Actively Exploited Flaw in Zimbra Collaboration Suite

The Cybersecurity and Infrastructure Security Agency (CISA) has issued a critical alert regarding an actively exploited vulnerability in Synacor’s Zimbra Collaboration Suite (ZCS), urging organizations to take immediate action to mitigate the threat.

The flaw, tracked as CVE-2019-9621, is a server-side request forgery (SSRF) vulnerability that resides in the ProxyServlet component of ZCS and has been added to CISA’s Known Exploited Vulnerabilities (KEV) catalog as of July 7, 2025.

What Is the Vulnerability?

CVE-2019-9621 allows remote attackers to exploit the ProxyServlet component in certain versions of Zimbra Collaboration Suite.

By leveraging this SSRF flaw, threat actors can force the server to make unauthorized requests to internal or external resources, potentially leading to remote code execution, data exfiltration, or further compromise of the affected system.

The vulnerability is classified as extremely high risk due to its potential impact and evidence of active exploitation in the wild.

Affected Versions

The ...