CVE-2026-73570
Zimbra Collaboration Suite (ZCS) OS Command Injection Vulnerability
Synacor Zimbra Collaboration Suite (ZCS)
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 as the Zimbra user.
Exploitation status
CISA Known Exploited Vulnerabilities
Listed by CISA on 21 August 2026. US federal agencies were required to remediate it by 24 August 2026.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 32.4%, which is higher than 98.3% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L
Frequently asked questions
Is CVE-2026-73570 being exploited by ransomware groups?
No ransomware group in this database is currently recorded as exploiting CVE-2026-73570.
What does CVE-2026-73570 affect?
CVE-2026-73570 affects Synacor Zimbra Collaboration Suite (ZCS). 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 as the Zimbra user.
How severe is CVE-2026-73570?
CVE-2026-73570 is rated HIGH with a CVSS base score of 8.9. EPSS puts the probability of exploitation in the next 30 days at 32.4%, higher than 98.3% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 24 August 2026.
How should organisations respond to CVE-2026-73570?
Apply the vendor patch for Synacor Zimbra Collaboration Suite (ZCS) as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.