Patch nowWhy this label: EPSS 72%

CVE-2026-73570Zimbra Collaboration Suite (ZCS) OS Command Injection Vulnerability

Product: Synacor Zimbra Collaboration Suite (ZCS)
Added to CISA KEV: August 21, 2026
Deadline for US federal agencies: August 24, 2026
Known ransomware use: Not known
EPSS, next 30 days: 72%, in the top 1% of scored CVEs (Oct 25, 2026)
Weakness: CWE-78

What CISA says

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.

What CISA asks you to do

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.

Sources

Also exploited recently

Data from CISA's Known Exploited Vulnerabilities catalog (public domain) and FIRST EPSS, refreshed hourly. Rheono did not find or test this vulnerability; this page summarizes public sources.