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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 28 Jul 2025.
Zimbra Collaboration SuiteApplication · Synacor

CVE-2019-9621

HIGH · 7.5 CVSS v3.1 Published 2019-04-30
Fix available
A fix is available. Upgrade to 8.6.0 / 8.7.11 or later.
See remediation →
100/100
Remediation priority · Urgent
In the wild High EPSS Public exploit Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Zimbra Collaboration Suite before 8.6 patch 13, 8.7.x before 8.7.11 patch 10, and 8.8.x before 8.8.10 patch 7 or 8.8.x before 8.8.11 patch 3 allows SSRF via the ProxyServlet component.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Zimbra Collaboration Suite contains a Server-Side Request Forgery (SSRF) vulnerability in the ProxyServlet component. The ProxyServlet fails to properly validate or restrict the URLs it forwards requests to, allowing an attacker to make the Zimbra server request arbitrary URLs. This can be exploited to access internal services, cloud metadata endpoints, or internal network resources that should not be exposed.

MitigationApply the appropriate Zimbra patch for the installed version: patch 13 for 8.6.x, patch 10 for 8.7.11, patch 7 for 8.8.10, or patch 3 for 8.8.11. As a compensating control, restrict network access to the ProxyServlet endpoint via firewall rules or WAF policies.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Zimbra Collaboration SuiteApplication
Affected:< 8.6.0>= 8.7.0, < 8.7.11>= 8.8.0, < 8.8.9= 8.6.0= 8.7.11= 8.8.9= 8.8.10= 8.8.11

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed Zimbra version
    Run '/opt/zimbra/bin/zmcontrol -v' or check '/opt/zimbra/.install_history' for version information. On Red Hat/CentOS also check 'rpm -qa | grep zimbra'
    Affected if Version is < 8.6.0, or between 8.7.0-8.7.11 inclusive, or between 8.8.0-8.8.11 inclusive, or equals 8.6.0, 8.7.11, 8.8.9, 8.8.10, or 8.8.11
  2. Confirm ProxyServlet endpoint is exposed
    Check if the web server exposes the ProxyServlet path. This is typically at '/service/proxy' or '/zimbraAdmin/proxy' relative to the Zimbra web root. Inspect the application server configuration files in /opt/zimbra/jetty*/webapps/ for servlet mappings
    Affected if ProxyServlet is accessible without additional authentication restrictions beyond normal Zimbra access controls
  3. Verify network accessibility of ProxyServlet
    From an external or less-trusted network perspective, attempt to reach the ProxyServlet endpoint (e.g., curl http://<server>/service/proxy) or review firewall/WAF rules that permit or block access to this endpoint
    Affected if The ProxyServlet endpoint can be reached from network segments where untrusted users can initiate requests

The environment is affected if Zimbra version is any release before 8.8.12 (including all 8.6.x, 8.7.x through 8.7.11, and 8.8.x through 8.8.11) AND the ProxyServlet component is accessible to the attacker via HTTP/HTTPS

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 8.6.0 / 8.7.11 / 8.8.9 or later
Fixed in 8.6.08.7.118.8.9
Interim mitigation

Apply the appropriate Zimbra patch for the installed version: patch 13 for 8.6.x, patch 10 for 8.7.11, patch 7 for 8.8.10, or patch 3 for 8.8.11. As a compensating control, restrict network access to the ProxyServlet endpoint via firewall rules or WAF policies.

Recommended fix High confidence

8.8.10 patch 7 or later (or 8.8.11 patch 3 or later)

  1. 1. Back up the current Zimbra Collaboration Suite installation and database
  2. 2. Identify the current ZCS version by running: zmcontrol -v
  3. 3. For ZCS 8.6.x: Upgrade to 8.6.0 patch 13 or later
  4. 4. For ZCS 8.7.x: Upgrade to 8.7.11 patch 10 or later
  5. 5. For ZCS 8.8.x: Upgrade to 8.8.10 patch 7 or later, OR 8.8.11 patch 3 or later
  6. 6. Download the appropriate patched version from the official Zimbra downloads portal (https://www.zimbra.com/download/)
  7. 7. Run the installation script as the root user: ./install.sh
  8. 8. After installation, verify the version: zmcontrol -v
Caveat Review ZCS 8.8.x release notes for any configuration or feature changes between versions; test in staging environment before production deployment

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Zimbra Collaboration Suite Exploited in the wild — priority engagement
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2019-9621 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data