Attackers Exploit Zimbra SNMP Flaw for Unauthenticated Remote Code Execution
CERT Polska and CISA report active exploitation of Zimbra RCE CVE-2026-73570, with 267 instances compromised per Shadowserver.
CVE-2026-73570 (CVSS 8.9) enables unauthenticated command injection and remote code execution in Zimbra Collaboration before 10.1.20 when the optional zimbra-snmp package is installed and SNMP notifications are enabled, via crafted SMTP requests. CISA added the flaw to its KEV catalog on August 21, 2026, with a federal patch deadline of August 24. The Shadowserver Foundation counted 267 compromised instances as of August 24, 2026, led by the US (46), Sweden (21), France (20) and Germany (17). Separately, Russia-linked Laundry Bear has weaponized Zimbra stored XSS CVE-2025-66376 against Western government and commercial mail servers since at least July 2025, delivering the ZimReaper payload.