---
id: "CVE-2019-9670"
kind: "vulnerability"
aliases: ["CVE-2019-9670"]
title: "Synacor Zimbra Collaboration Suite (ZCS): Synacor Zimbra Collaboration Suite (ZCS) Improper Restriction of XML External Entity Reference"
severity: "critical"
cvss: 9.8
epss: 0.99986
exploited: true
status: "open"
category: "package"
products: [{"name": "Synacor Zimbra Collaboration Suite (ZCS)", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["exploited", "mail-server", "package", "self-hosted", "zimbra"]
not_affected_if: ["managed-hosting"]
published_at: "2019-05-29T22:29:01+00:00"
first_seen_at: "2026-10-23T19:11:53+00:00"
updated_at: "2026-10-23T21:57:35+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2019-9670", "first_seen_at": "2026-10-23T19:11:53+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2019-9670", "first_seen_at": "2026-10-23T19:13:44+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2019-9670", "first_seen_at": "2026-10-23T21:57:35+00:00"}]
---

# Synacor Zimbra Collaboration Suite (ZCS): Synacor Zimbra Collaboration Suite (ZCS) Improper Restriction of XML External Entity Reference

Zimbra Collaboration Suite has an XML external entity (XXE) flaw in its mailboxd component, which is the core mail server process. An attacker can send crafted XML to make the server read local files or reach internal network resources.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:Synacor Zimbra Collaboration Suite (ZCS) affected ? fixed ?

## Fix

Apply the Zimbra updates that address CVE-2019-9670 per vendor instructions, as directed by CISA.

## Timeline

- 2026-10-23T19:11:53+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2019-9670
- 2026-10-23T19:13:44+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2019-9670
- 2026-10-23T21:57:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2019-9670

## From the sources

Synacor Zimbra Collaboration Suite (ZCS) contains an improper restriction of XML external entity (XXE) vulnerability in the mailboxd component.

CISA required action: Apply updates per vendor instructions.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_