Zimbra Collaboration Suite

CISA Adds Actively Exploited Zimbra CVE-2026-73570 to KEV Catalog with Immediate Patching Deadline

CISA has added CVE-2026-73570 affecting Zimbra Collaboration Suite to its Known Exploited Vulnerabilities catalog, ordering urgent remediation due to confirmed active exploitation. The flaw enables unauthenticated remote command execution on servers where the optional zimbra-snmp package is installed and SNMP notifications are enabled. Exploitation occurs via specially crafted SMTP requests that trigger operating system command injection under the privileges of the zimbra user. Zimbra released the fix in version 10.1.20 on July 20, 2026, while CISA placed the vulnerability in the KEV list on August 21 and set an August 24 deadline for federal civilian agencies. Organizations are advised to first verify exposure by checking for zimbra-snmp and SNMP notification settings before applying the update. Post-patch steps include validating the version, controlled service restarts, and hunting for indicators such as unexpected Zimbra restarts, anomalous zimbra user activity, and new files in sensitive directories like /opt/zimbra/jetty/webapps/. The directive highlights the critical nature of pre-authentication flaws in internet-facing mail servers that process untrusted inbound traffic.