CVE-2021-42090
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. The Form functionality allows remote code execution because deserialization is mishandled.
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 confidenceZammad before version 4.1.1 contains a deserialization vulnerability in its Form functionality that allows unauthenticated remote attackers to execute arbitrary code on the target system. The mishandled deserialization process enables attackers to craft malicious payloads that deserialize into executable code.
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
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/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 checksWork through these to decide whether this CVE applies to you.
-
Verify Zammad installation existsLocate Zammad installation directories or check running processes for Zammad components (e.g., look for Zammad web application files, services, or Docker containers)Affected if Zammad is not found in the environment, this CVE does not apply
-
Determine installed Zammad versionAccess the Zammad admin interface and navigate to the About or System Information page to view the version number, or check the version file in the Zammad installation directoryAffected if The version is less than 4.1.1 (e.g., 4.0.x, 3.x, etc.)
-
Confirm Form functionality is enabledCheck Zammad admin settings under Apps > Forms or Settings > Forms to see if any forms are active, or inspect the configuration for enabled form endpointsAffected if Forms are enabled and accessible to unauthenticated users
The environment is affected if Zammad version is below 4.1.1 AND the Form functionality is enabled or accessible.
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 remediate this vulnerability. If immediate upgrading is not feasible, consider disabling or restricting access to the Form functionality as a temporary compensating control.
Zammad 4.1.1 or later
- 1. Back up your Zammad instance and database before upgrading
- 2. Check your current Zammad version (typically in Admin > System > Information or via command line)
- 3. Upgrade Zammad to version 4.1.1 or later following the official upgrade guide for your installation method
- 4. Verify the upgrade was successful by checking the version number
- 5. Test the Form functionality to ensure it works correctly after upgrade
- 6. Monitor logs for any unusual activity that may indicate exploitation attempts prior to patching
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation3.0 h
- Implementation6.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,984.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-42090 — 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-2021-42090 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
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.
- 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