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

Synacor · Zimbra Collaboration Suite (ZCS)

Listed by CISA as exploited in the wild since 21 Aug 2026. Below: exploitation status, EPSS and every published CVSS, each with its source, then affected versions and references.

Build snapshot collected · KEV catalog 2026.10.02 · EPSS of 2 Oct 2026 · not a live feed: collected once, at build time

Description

as written by CISA (KEV catalog)

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.

Required action

CISA KEV

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.

Affected products and versions

CVE record · mitre

  • Zimbra · Collaboration

    • affected: before 10.1.20

Status words (affected, unaffected, unknown) and version bounds are copied from the record. An upper bound such as “before 7.1.0” usually marks the first fixed version; confirm in the vendor advisory before planning an upgrade.

References

CISA KEV notes and CVE record

EPSS over the last 30 days

See also: the full KEV catalog

Related entries

Added in the same week

Questions about CVE-2026-73570

Is CVE-2026-73570 being exploited?

Yes, according to CISA. CVE-2026-73570 was added to the Known Exploited Vulnerabilities catalog on 21 Aug 2026, which CISA does only with reliable evidence of exploitation in the wild. The catalog field for ransomware campaign use says "Unknown".

What is the deadline to remediate CVE-2026-73570?

CISA set 24 Aug 2026 as the due date for US Federal Civilian Executive Branch agencies. The date is binding only for those agencies; other organisations can read it as a measure of urgency.

What is the EPSS score of CVE-2026-73570?

11.7%, in the 96th percentile, in the FIRST EPSS model of 2 Oct 2026. It estimates the probability of exploitation activity in the following 30 days. For a CVE already in KEV the score is secondary: exploitation has been observed.

How severe is CVE-2026-73570?

mitre.org rates it 8.9 HIGH (CVSS 3.1). These are the published assessments as of 3 Oct 2026; this site does not rescore.

Which product does CVE-2026-73570 affect?

Synacor Zimbra Collaboration Suite (ZCS), as named in the CISA catalog. The affected versions listed in the CVE record are on this page; the vendor advisory in the references is the authority on fixed versions.

Related sections