— Unscored

Zimbra Collaboration Suite (ZCS) OS Command Injection Vulnerability

CVE-2026-73570 Exploited

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.

Being exploited in the wild

Catalogued 21 August 2026 · US federal remediation deadline 24 August 2026

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…

Exploit code is also public: Public PoC · Nuclei template

NucleiZimbra Collaboration Suite < 10.1.20 - OS Command Injection
Public PoCHORKimhab/CVE-2026-735705 stars
Public PoCjishino567/CVE-2026-735704 stars
Public PoCgabrielunknown/CVE-2026-735704 stars
Public PoCdahnutz/zimbra-cve-2026-73570-ir2 stars
Public PoC0xBlackash/CVE-2026-735702 stars
Public PoCBiuTrap/CVE-2026-73570
Public PoCINFOKOM-KI/Zimbra-CVE-2026-73570-Rules
Public PoCjuanpoch/CVE-2026-73570

Assessment

CVSS: Not yet scored
Severity: Unscored
Known exploited: Yes — listed in the CISA KEV catalog
Exploit availability: CISA KEV, Public PoC, Nuclei template
Published: 21 August 2026
Last updated: 21 August 2026
Affected: Synacor · Zimbra Collaboration Suite (ZCS)
Weakness: CWE-78

At the source

CISA KEV

References

https://www.cisa.gov/known-exploited-vulnerabilities-catalog

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