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Zimbra Collaboration SuiteApplication · Synacor

CVE-2026-33372

MEDIUM · 5.4 CVSS v3.1 Published 2026-03-20
Fix available
A fix is available. Upgrade to 10.1.16 or later.
See remediation →
61/100
Remediation priority · Elevated
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
An issue was discovered in Zimbra Collaboration (ZCS) 10.0 and 10.1. A cross-site request forgery (CSRF) vulnerability exists in Zimbra Webmail due to improper validation of CSRF tokens. The application accepts CSRF tokens supplied within the request body instead of requiring them through the expected request header. An attacker can exploit this issue by tricking an authenticated user into submitting a crafted request. This may allow unauthorized actions to be performed on behalf of the victim.

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 CSRF vulnerability in Zimbra Webmail (versions 10.0 and 10.1) allows attackers to bypass protection by submitting CSRF tokens in the request body rather than the required HTTP header. The application improperly validates tokens passed in the request body, enabling authenticated users to be tricked into executing unauthorized actions via crafted requests.

MitigationImplement proper CSRF token validation requiring tokens in the HTTP header (e.g., X-CSRF-Token) and reject tokens submitted in the request body; apply SameSite cookie attributes and origin/referer validation as additional defense-in-depth measures.

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:>= 10.0.0, < 10.1.16

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
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/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 installed Zimbra version
    Run 'zmcontrol -v' or check '/opt/zimbra/.git.describe' to retrieve the installed Zimbra Collaboration Suite version
    Affected if Version is 10.0.0 through 10.1.15 (anything >= 10.0.0 but < 10.1.16)
  2. Confirm Zimbra Webmail is accessible
    Verify the Zimbra web client is running and accessible by accessing the webmail login page
    Affected if Webmail interface is exposed and operational
  3. Check CSRF token handling configuration
    Review Zimbra proxy configuration files (nginx.template or nginx.conf) in /opt/zimbra/conf/nginx/ to see how CSRF tokens are configured to be validated
    Affected if Configuration shows tokens can be passed in request body without validation against the required HTTP header
  4. Test token validation behavior
    Submit a test request to the webmail API endpoint with a CSRF token in the request body (e.g., as a form parameter) rather than the X-CSRF-Token HTTP header and observe if the request is accepted
    Affected if Requests with tokens only in the body are accepted without rejecting based on missing header-based token validation

Your environment is affected if Zimbra Collaboration Suite version is 10.0.0 through 10.1.15 and the webmail accepts CSRF tokens submitted in the request body without requiring them in the X-CSRF-Token HTTP header.

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 10.1.16 or later
Fixed in 10.1.16
Interim mitigation

Implement proper CSRF token validation requiring tokens in the HTTP header (e.g., X-CSRF-Token) and reject tokens submitted in the request body; apply SameSite cookie attributes and origin/referer validation as additional defense-in-depth measures.

Recommended fix Moderate confidence

Zimbra Collaboration Suite 10.1.16 or later

  1. Backup the Zimbra Collaboration Suite installation and all associated data
  2. Plan a maintenance window for the upgrade process
  3. Download Zimbra Collaboration Suite version 10.1.16 or later from the official Zimbra repository
  4. Stop all Zimbra services before beginning the upgrade
  5. Upgrade Zimbra to version 10.1.16 or later using the official upgrade procedure
  6. Restart all Zimbra services after the upgrade completes
  7. Verify that the webmail interface is accessible and functional
  8. Confirm that CSRF tokens are now properly validated through request headers rather than request body
Caveat Standard upgrade risks apply - review Zimbra release notes for any configuration or feature changes between your current version and 10.1.16

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

Fix this in Zimbra Collaboration Suite Scoped from the published advisory
  • Consultation4.0 h
  • Implementation12.0 h
  • Testing8.0 h
  • Review / QA4.0 h
28.0 hours of engineering $4,880
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,808.

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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-2026-33372 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