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CVE-2026-73570

Zimbra Collaboration Suite (ZCS) OS Command Injection Vulnerability

Synacor Zimbra Collaboration Suite (ZCS)Applications & CMS
Open in ThreatlineRecord JSON
CVSS
8.9High
ExploitationExploited in the wildAdded to KEV 21 Aug 2026CISA KEV
Exploit odds (EPSS)71.7%Chance of exploitation activity in the next 30 days, higher than 99% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in10.1.20Fixed versionCVE List
Federal deadline24 Aug 2026Remediation due date for US federal agenciesCISA KEV
CISA required actionApply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines. CISA KEV
Patching is not enoughCISA requires federal agencies to look for signs of compromise on affected systems, not only patch (forensic triage under BOD 26-04). Treat exposed systems as possibly compromised. CISA guidance

What fixes it

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

Timeline

  1. 13 Aug 2026, 15:19 UTCPublishedCVE List
  2. 21 Aug 2026Added to CISA KEVCISA KEV

Public exploit code and templates 1

  • Scanner templateZimbra Collaboration Suite < 10.1.20 - OS Command InjectionNuclei

Listed so defenders can prioritize. Threatline links to the source and does not host exploit code.

Description

Zimbra Collaboration Suite (ZCS) contains an OS command injection vulnerability which could allow an unauthenticated attacker to send specially crafted SMTP requests that may result in execution of arbitrary operating system commands as the Zimbra user.

Text from CVE List

Affected versions 1

  • Collaborationaffected: all versions before 10.1.20CVE List

References 6