Zimbra Collaboration Suite (ZCS) OS Command Injection Vulnerability (CVE-2026-73570)
Severity: high · Patch status: unknown · Since 2026-08-21 · CVE-2026-73570
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. CISA added CVE-2026-73570 to its Known Exploited Vulnerabilities catalog on Aug 21, 2026, which means attackers are exploiting it in the wild.
What to do
- 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.
- US federal agencies must remediate by Aug 24, 2026 (BOD 22-01); treat that as the outer limit.
Sources
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