Zimbra Collaboration Suite (ZCS) OS Command Injection Vulnerability

Are you affected?

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• cpe synacor/zimbra collaboration suiteversion unspecified
• vendor Synacor Zimbra Collaboration Suite (ZCS)version unspecified

How to fix CVE-2026-73570

• Recommended remediation

  Apply 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 due date Aug 24, 2026.

• Official advisories

  • CISA KEV · cisa.gov
  • CVE.org · cve.org
  • FIRST EPSS · first.org
  • Microsoft Threat Intelligence · microsoft.com
  • NIST NVD · nvd.nist.gov
  • VulnCheck KEV · vulncheck.com

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

1. Aug 13, 2026 · Catalog

   Detected

   A remote code execution vulnerability exists in Zimbra Collaboration (ZCS) before 10.1.20 when the optional zimbra-snmp package is installed and SNMP notifications are enabled. Due to improper sanitization of untrusted input during SNMP notification processing, an unauthenticated attacker can send specially crafted SMTP requests that may result in execution of arbitrary operating system commands a

2. Aug 21, 2026 · CISA KEV

   Known exploited

   Apply 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

3. Aug 24, 2026 · CISA KEV

   Remediation due

   Apply 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

4. Aug 24, 2026 · Catalog

   Updated

   A remote code execution vulnerability exists in Zimbra Collaboration (ZCS) before 10.1.20 when the optional zimbra-snmp package is installed and SNMP notifications are enabled. Due to improper sanitization of untrusted input during SNMP notification processing, an unauthenticated attacker can send specially crafted SMTP requests that may result in execution of arbitrary operating system commands a

Sources

• CISA KEVConfirmed exploitationCVE-2026-73570

  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.

  cisa.gov
• CVE.orgVulnerability recordCVE-2026-73570

  Official CVE identifier

  cve.org
• FIRST EPSSExploitation probabilityCVE-2026-73570

  30-day exploitation probability 71.7%

  first.org
• Microsoft Threat IntelligenceThreat researchCVE-2026-73570

  Research mention from Microsoft Threat Intelligence. Not confirmation of exploitation.

  microsoft.com
• NIST NVDVulnerability recordCVE-2026-73570

  A remote code execution vulnerability exists in Zimbra Collaboration (ZCS) before 10.1.20 when the optional zimbra-snmp package is installed and SNMP notifications are enabled. Due to improper sanitization of untrusted input during SNMP notification processing, an unauthenticated

  nvd.nist.gov
• VulnCheck KEVConfirmed exploitationCVE-2026-73570

  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.

  vulncheck.com

References

• CISA note · blog.zimbra.com
• VulnCheck exploitation evidence · dashboard.shadowserver.org
• VulnCheck exploitation evidence · dashboard.shadowserver.org
• VulnCheck exploitation evidence · dashboard.shadowserver.org
• Third Party Advisory · moje.cert.pl
• CISA note · nvd.nist.gov
• VulnCheck exploitation evidence · previdian.com
• Release Notes · wiki.zimbra.com
• CISA note · wiki.zimbra.com
• US Government Resource · cisa.gov
• CISA note · cisa.gov
• CISA note · cisa.gov
• VulnCheck exploitation evidence · cisa.gov

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.