ZeroHour
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Zimbra Collaboration Suite

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CISA Warns of Zimbra OS Command Injection Vulnerability Active Exploitation (CVE-2026-73570)

CISA added actively exploited Zimbra OS command injection flaw CVE-2026-73570 to its KEV catalog, urging users to patch by August 24, 2026.

CISA warned that Zimbra vulnerability CVE-2026-73570 is being actively exploited in the wild and added it to its Known Exploited Vulnerabilities Catalog. The OS command injection flaw resides in the SNMP monitoring component and is exploitable when SNMP notifications are enabled. Users, including US federal agencies subject to BOD deadlines, were urged to apply fixes before the August 24, 2026 deadline. Qualys ThreatPROTECT published tracking coverage of the KEV addition.

Qualys ThreatPROTECT · 21d agoExploit / PoC in the wildCVE-2026-73570

Unpatched Zimbra servers are falling to CVE-2026-73570 attacks

Attackers are exploiting unpatched Zimbra servers via CVE-2026-73570; 274 instances compromised, and CISA added the flaw to its KEV catalog.

The Shadowserver Foundation counted at least 274 compromised internet-facing Zimbra Collaboration Suite instances exploited through CVE-2026-73570, up from 155 on August 20. The unauthenticated code injection flaw affects servers with the optional zimbra-snmp package and SNMP notifications enabled, allowing arbitrary OS command execution via crafted SMTP requests. Synacor patched the issue in ZCS v10.1.20 on July 20, 2026, and at least 8,200 instances remain unpatched. CISA added the flaw to its Known Exploited Vulnerabilities catalog and gave US federal civilian agencies three days to remediate and check for compromise.

Help Net Security · 21d agoExploit / PoC in the wildCVE-2026-735701

U.S. CISA adds Zimbra Collaboration Suite (ZCS) flaw to its Known Exploited Vulnerabilities catalog

CISA added actively exploited Zimbra flaw CVE-2026-73570 (unauthenticated OS command injection RCE) to its KEV catalog, setting an August 24, 2026 federal patch deadline.

CISA added CVE-2026-73570, an unauthenticated OS command injection flaw in Zimbra Collaboration Suite, to its Known Exploited Vulnerabilities catalog after CERT Polska confirmed active exploitation. The flaw lets attackers execute shell commands as the zimbra user via the snmp_notify parameter when the SNMP trap service is enabled and the default swatchdog service is running. Zimbra patched the issue in version 10.1.20 released July 20, 2026, 28 days before exploitation was confirmed. Under BOD 22-01, federal civilian agencies must patch by August 24, 2026.

Security Affairs · 24d agoExploit / PoC in the wildCVE-2026-73570

Poland's CERT Warns of Active Exploitation of Critical Zimbra Collaboration Suite Flaw

CERT Polska confirms active exploitation of critical unauthenticated RCE CVE-2026-73570 in Zimbra Collaboration Suite, patched July 20.

CERT Polska confirmed threat actors are actively exploiting CVE-2026-73570, an unauthenticated OS command injection in Zimbra Collaboration Suite allowing arbitrary shell commands as the zimbra user. Exploitation requires the SNMP trap service via snmp_notify with swatchdog running, which is enabled by default; Shadowserver tracks over 12,100 internet-exposed Zimbra servers. Zimbra fixed the flaw in version 10.1.20 on July 20, 2026, 28 days before exploitation was confirmed. Historical Zimbra targeting includes Winter Vivern, APT29, and APT28 campaigns.

Security Affairs · 25d agoExploit / PoC in the wildCVE-2026-73570

Related CVEs

  • Unauthenticated OS Command Injection RCE in Synacor Zimbra Collaboration Suite
    CVE-2026-73570 is an OS command injection vulnerability (CWE-78) in Synacor Zimbra Collaboration Suite (ZCS) before 10.1.20, caused by improper sanitization of untrusted input during SNMP notification processing. It is triggered when the optional zimbra-snmp package is installed and SNMP notifications are enabled: an unauthenticated attacker sends specially crafted SMTP requests that the flawed notification path turns into execution of arbitrary operating system commands. Successful exploitation runs commands as the Zimbra user, giving attackers control of the mail server's service account with high confidentiality and integrity impact across the host. Only ZCS deployments running the optional SNMP component with notifications enabled are vulnerable; other Zimbra installs are not exposed to this specific flaw. The flaw is under active exploitation: CISA added it to the KEV catalog on 2026-08-21, Poland's CERT has warned of in-the-wild attacks, unpatched Zimbra servers are reported compromised, and two public proof-of-concept exploits exist.
    · Synacor Zimbra Collaboration Suite (ZCS) before 10.1.20 (when the optional zimbra-snmp package is installed and SNMP notifications are enabled) KEV PoC ×4large

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