CVE-2026-40874
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 · uneditedmailcow: dockerized is an open source groupware/email suite based on docker. In versions prior to 2026-03b, no administrator verification takes place when deleting Forwarding Hosts with `/api/v1/delete/fwdhost`. Any authenticated user can call this API. Checks are only applied for edit/add actions, but deletion can still significantly disrupt the mail service. Version 2026-03b fixes the vulnerability.
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 confidenceThe mailcow API endpoint `/api/v1/delete/fwdhost` lacks administrator verification, allowing any authenticated user to delete forwarding hosts. This can disrupt mail service as forwarding host deletion affects email routing.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
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
- High
- Privileges
- Low
- Authentication
- X
- User interaction
- None
- Scope
- X
CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
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 checksWork through these to decide whether this CVE applies to you.
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Identify if mailcow is installedCheck for mailcow installation by looking for docker-compose.yml file, mailcow directory, or running 'docker ps' to list mailcow containersAffected if Mailcow is not installed - the CVE does not apply
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Check installed mailcow versionLook for the mailcow version file typically found at /opt/mailcow/docker-compose.yml or check the UI footer for version number. Also check 'grep VERSION /opt/mailcow/mailcow.conf' if the configuration file existsAffected if Version is lower than 2026-03b (e.g., 2026-03a, 2026-02b, or earlier releases)
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Verify API endpoint access controlTest the /api/v1/delete/fwdhost endpoint with a non-administrator authenticated user account. Submit a valid API token for a regular user and attempt to access the endpoint. Check the HTTP response code and whether the request is processed or rejectedAffected if A non-admin user can successfully access and execute the delete operation on /api/v1/delete/fwdhost without receiving a 403 Forbidden or admin-required error
A user is affected if they are running mailcow versions earlier than 2026-03b AND the API endpoint /api/v1/delete/fwdhost accepts requests from non-administrator authenticated users without proper authorization checks.
Generated from the published advisory. Verify against your own configuration.
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 · scopedUpgrade to mailcow version 2026-03b or later, which implements proper administrator verification for the forwarding host deletion API endpoint.
2026-03b
- Back up your current mailcow installation and configuration
- Update your mailcow Docker images to the latest version
- Run the mailcow update script to apply the 2026-03b release
- Verify the API endpoint `/api/v1/delete/fwdhost` now requires administrator verification
- Test that only admin users can delete Forwarding Hosts
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-40874 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-40874 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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
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