CVE-2021-42084
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 · uneditedAn issue was discovered in Zammad before 4.1.1. An attacker with valid agent credentials may send a series of crafted requests that cause an endless loop and thus cause denial of service.
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 · moderate confidenceAn authenticated agent user with valid credentials can send crafted requests to Zammad before version 4.1.1 that trigger an infinite loop in the application, causing denial of service by making the system unresponsive.
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< 4.1.1CVSS 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
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/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 checksWork through these to decide whether this CVE applies to you.
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Confirm Zammad installationLocate the Zammad installation directory or verify access to the Zammad web interface at your configured URL.Affected if Zammad is not present or the web interface cannot be accessed.
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Determine installed Zammad versionCheck the Zammad version via the web interface (typically in Admin > System > Information) or by running 'zammad --version' if the CLI is available. Check for a version file in the installation directory if accessible.Affected if The installed version is below 4.1.1.
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Verify agent authentication is enabledConfirm that agent user authentication is configured and active in Zammad. This vulnerability requires a valid authenticated agent user account. Check in the admin interface that agent roles are enabled and agent users exist.Affected if Agent authentication is enabled and there are active agent user accounts.
The environment is affected if Zammad version is below 4.1.1 and agent user authentication is enabled, allowing a valid agent to trigger the infinite loop.
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 · scoped4.1.1
Upgrade Zammad to version 4.1.1 or later to patch the infinite loop vulnerability.
Zammad 4.1.1 or later
- 1. Create a complete backup of the Zammad database and configuration files
- 2. Stop the Zammad service (e.g., systemctl stop zammad)
- 3. Update the package repository and upgrade Zammad to version 4.1.1 or later using the appropriate package manager (apt-get update && apt-get install zammad or yum update zammad)
- 4. Run database migrations if required (zammad run rails db:migrate)
- 5. Clear any caches (zammad cache:clear)
- 6. Restart the Zammad service (e.g., systemctl start zammad)
- 7. Verify the application is functioning correctly and the vulnerability is resolved
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation3.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,272.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-42084 — 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-2021-42084 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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