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Zimbra Collaboration SuiteApplication · Synacor

CVE-2016-9924

CRITICAL · 9.8 CVSS v3.0 Published 2017-03-29
Fix available
A fix is available. Upgrade to after 8.7.3 or later.
See remediation →
100/100
Remediation priority · Urgent
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 (ZCS) before 8.7.4 allows remote attackers to conduct XML External Entity (XXE) attacks.

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 before 8.7.4 contains an XML External Entity (XXE) injection vulnerability in its XML parsing implementation. Attackers can send specially crafted XML requests containing external entity references to read arbitrary files on the server, perform SSRF attacks, or cause denial of service.

MitigationUpgrade Zimbra Collaboration Suite to version 8.7.4 or later. As a workaround, disable external entity processing in the XML parser configuration and implement input validation for XML payloads.

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:<= 8.7.3

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
High
Availability
High

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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. Determine Zimbra Collaboration Suite installed version
    Run the Zimbra version command (zmcontrol -v or zmmsgtrace --version) or check the installed packages list for zimbra-core
    Affected if Installed version is 8.7.3 or earlier (any version <= 8.7.3)
  2. Identify XML processing endpoints
    Review Zimbra configuration files (localconfig.xml) and web service endpoints that accept XML input, such as the SOAP interface and admin console
    Affected if XML input handling is enabled on any exposed endpoint
  3. Verify XML parser external entity configuration
    Examine the XML parser configuration in Zimbra's JavaMail settings or the underlying XML processing library configuration to determine if external entity processing is permitted
    Affected if External entity processing is enabled or set to allow DTD processing in the XML parser
  4. Check for XXE-vulnerable XML handling code
    Review Zimbra logs or capture a sample XML request to the affected service and analyze how the XML is parsed (look for whether DTDs are processed)
    Affected if The XML parser processes DTDs and resolves external entity references

A user is affected if they are running Zimbra Collaboration Suite version 8.7.3 or earlier AND the XML parser is configured to process external entities or DTDs.

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 a release after 8.7.3
Interim mitigation

Upgrade Zimbra Collaboration Suite to version 8.7.4 or later. As a workaround, disable external entity processing in the XML parser configuration and implement input validation for XML payloads.

Recommended fix High confidence

Zimbra Collaboration Suite 8.7.4

  1. 1. Perform a complete backup of the Zimbra mailbox, database, and configuration data
  2. 2. Verify system prerequisites and ensure the operating system is supported by ZCS 8.7.4
  3. 3. Download Zimbra Collaboration Suite 8.7.4 from the official Zimbra repository
  4. 4. Stop all Zimbra services before beginning the upgrade process
  5. 5. Run the ZCS 8.7.4 installer as the root user: ./install.sh
  6. 6. Follow the installer prompts to complete the upgrade
  7. 7. Verify all Zimbra services started successfully after upgrade
  8. 8. Confirm the XXE vulnerability is resolved by checking the Zimbra version: zmcontrol -v
Caveat Review ZCS 8.7.4 release notes for any configuration or feature changes from earlier 8.7.x versions before upgrading

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

Fix this in Zimbra Collaboration Suite Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing10.0 h
  • Review / QA6.0 h
34.0 hours of engineering $5,940
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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-2016-9924 in production — separate from our analysis above.

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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