CVE-2026-73570 - Zimbra Collaboration Suite (ZCS) OS Command Injection Vulnerability

Technical Severity

CVSS v3.1 Metrics

HIGH

8.9 / 10

Minimal Risk Critical

Vector Specification

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L

Exploitation Likelihood

EPSS Prediction

20.53 %

Predictive Probability

Percentile Rank

97.3 th

Documented as more likely to be exploited than 97.3% of known CVEs.

Detection Date

Aug 21, 2026

Remediation Due

Aug 24, 2026

CISA Catalog Active

Threat Analysis

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.

Remediation Directive

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 evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

External Intelligence

https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories

https://blog.zimbra.com/2026/07/patch-release-update-zimbra-10-1-20/

CISA

CISA Advisory

https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk

CISA

CISA Advisory

https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk

NVD

National Vulnerability Database

https://nvd.nist.gov/vuln/detail/CVE-2026-73570