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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 10 May 2022. Known ransomware use
Zimbra Collaboration SuiteApplication · Synacor

CVE-2018-6882

MEDIUM · 6.1 CVSS v3.1 Published 2018-03-27
Fix available
A fix is available. Upgrade to 8.7.0 or later.
See remediation →
100/100
Remediation priority · Urgent
In the wild Ransomware Public exploit Remotely reachable No privileges

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
Cross-site scripting (XSS) vulnerability in the ZmMailMsgView.getAttachmentLinkHtml function in Zimbra Collaboration Suite (ZCS) before 8.7 Patch 1 and 8.8.x before 8.8.7 might allow remote attackers to inject arbitrary web script or HTML via a Content-Location header in an email attachment.

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

A stored cross-site scripting (XSS) vulnerability exists in Zimbra Collaboration Suite's ZmMailMsgView.getAttachmentLinkHtml function. Attackers can inject malicious scripts via the Content-Location header in email attachments, which are then rendered without proper sanitization when other users view the attachment.

MitigationUpgrade ZCS to version 8.7 Patch 1 or later, or 8.8.7 or later. As a temporary measure, disable or restrict handling of external email attachments until patching is completed.

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:< 8.7.0= 8.7.0= 8.8.0= 8.8.1= 8.8.2= 8.8.3= 8.8.4= 8.8.5= 8.8.6

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
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/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 if Zimbra is installed
    Check for Zimbra processes running on the server using 'ps aux | grep zimbra' or look for /opt/zimbra directory
    Affected if Zimbra processes are running or the /opt/zimbra directory exists on the server
  2. Determine the installed ZCS version
    Run '/opt/zimbra/bin/zmcontrol -v' as the zimbra user, or check /opt/zimbra/zmversion.txt
    Affected if The reported version is 8.7.0, 8.8.0 through 8.8.6, or any version below 8.7.0
  3. Verify the web client interface is enabled
    Check if the Zimbra web service is running with 'zmcontrol status' or by reviewing the nginx or Apache proxy configuration
    Affected if The Zimbra web mail interface (Zimbra Web Client) is enabled and accessible to users
  4. Confirm users can view email attachments
    Review Zimbra mailbox configuration and verify that the attachment viewing feature is not globally disabled via zimbraMailDisabledAttachmentTypes
    Affected if Users have the ability to view email attachments through the web interface

The environment is affected if Zimbra Collaboration Suite version 8.7.0 through 8.8.6 or any version below 8.7.0 is installed, the web mail interface is enabled, and users can view email attachments through the web client.

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 8.7.0 or later
Fixed in 8.7.0
Interim mitigation

Upgrade ZCS to version 8.7 Patch 1 or later, or 8.8.7 or later. As a temporary measure, disable or restrict handling of external email attachments until patching is completed.

Recommended fix High confidence

8.7 Patch 1 or later, or 8.8.7 and later

  1. Identify current Zimbra Collaboration Suite version using the admin console or CLI: `zmcontrol -v`
  2. If running version 8.7.0, upgrade to 8.7 Patch 1 or later
  3. If running version 8.8.0 or 8.8.1, upgrade to 8.8.7 or later
  4. After upgrade, verify the ZmMailMsgView.getAttachmentLinkHtml function is patched by checking the Zimbra changelog for security fixes
  5. Test that Content-Location headers in email attachments are properly sanitized
Caveat Review Zimbra upgrade documentation for potential compatibility issues with existing configurations and integrations

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
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,088.

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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-2018-6882 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