Critical

Unpatched Zimbra servers are falling to CVE-2026-73570 attacks

Help Net Security

August 25, 2026 at 10:03 AM

Actively Exploited

Overview

At least 274 Zimbra servers have been compromised by attackers exploiting a vulnerability identified as CVE-2026-73570. This particular flaw is a code injection issue in the Zimbra Collaboration Suite (ZCS), which is widely used by organizations that prefer to manage their own data instead of relying on more expensive services like Microsoft 365 or Google Workspace. The vulnerability was patched by Synacor in version 10.1.20 of ZCS, released on July 20, 2026. However, many instances remain unpatched, leaving them vulnerable to exploitation. This incident highlights the risks associated with not keeping software updated, especially for platforms that handle sensitive communication and collaboration.

Key Takeaways

Active Exploitation: This vulnerability is being actively exploited by attackers. Immediate action is recommended.
Affected Systems: Zimbra Collaboration Suite (ZCS) versions prior to 10.1.20
Action Required: Upgrade to ZCS version 10.
Timeline: Disclosed on July 20, 2026

Original Article Summary

At least 274 internet-facing Zimbra instances have been compromised by unknown attackers via CVE-2026-73570, the Shadowserver Foundation shared on Monday. About CVE-2026-73570 Zimbra Collaboration Suite (ZCS) is a communication and collaboration platform popular with organizations that need to have control over their data or can’t afford a pricy alternative service like Microsoft 365 or Google Workspace. CVE-2026-73570 is a code injection flaw Synacor patched in ZCS v10.1.20, released on July 20, 2026. The vulnerability was … More → The post Unpatched Zimbra servers are falling to CVE-2026-73570 attacks appeared first on Help Net Security.

Impact

Zimbra Collaboration Suite (ZCS) versions prior to 10.1.20

Exploitation Status

This vulnerability is confirmed to be actively exploited by attackers in real-world attacks. Organizations should prioritize patching or implementing workarounds immediately.

Timeline

Disclosed on July 20, 2026

Remediation

Upgrade to ZCS version 10.1.20 or later to patch the CVE-2026-73570 vulnerability.

Additional Information

This threat intelligence is aggregated from trusted cybersecurity sources. For the most up-to-date information, technical details, and official vendor guidance, please refer to the original article linked below.

Related Topics: This incident relates to CVE, Microsoft, Google, and 1 more.

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