DrupalCMS
CVE-2017-6921
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 · uneditedIn Drupal 8 prior to 8.3.4; The file REST resource does not properly validate some fields when manipulating files. A site is only affected by this if the site has the RESTful Web Services (rest) module enabled, the file REST resource is enabled and allows PATCH requests, and an attacker can get or register a user account on the site with permissions to upload files and to modify the file resource.
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 file REST resource in Drupal 8 prior to 8.3.4 fails to properly validate certain fields when manipulating files via PATCH requests. This improper validation could allow an authenticated user with file upload and file resource modification permissions to perform unintended operations on files.
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
DrupalCMS
>= 8.0.0, < 8.3.4CVSS 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
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- High
- Availability
- None
CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/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 checksWork through these to decide whether this CVE applies to you.
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Check Drupal core versionNavigate to /admin/reports/status or check the composer.json file in your Drupal root directory to identify the installed Drupal 8 version.Affected if The installed version is less than 8.3.4 (e.g., 8.0.x, 8.1.x, 8.2.x, or 8.3.0-8.3.3).
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Verify RESTful Web Services module is enabledNavigate to /admin/modules and look for 'RESTful Web Services' (rest module) in the list, or check for 'rest' in the core.extension configuration via Drush: drush config-export | grep -i rest.Affected if The RESTful Web Services module is currently enabled.
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Confirm file REST resource is configuredCheck the REST resource configuration at /admin/config/services/rest or via Drush: drush config-get rest.settings resources. Look for 'entity:file' in the enabled resources.Affected if The file REST resource (entity:file) is listed as an enabled REST resource.
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Check if PATCH method is allowed for file resourceExamine the REST resource configuration to see which HTTP methods are permitted for the file resource. This can be viewed at /admin/config/services/rest or via the REST UI module if installed.Affected if PATCH method is enabled for the file REST resource, allowing authenticated users to modify files via PATCH requests.
A user is affected if they are running Drupal 8.0.0 to 8.3.3, have the RESTful Web Services module enabled with the file REST resource configured to accept PATCH requests, allowing authenticated users with file permissions to make unintended file modifications.
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.
From vendor data8.3.4
Disable the RESTful Web Services module if unused, or restrict the file REST resource from accepting PATCH requests. If the module is required, update Drupal to version 8.3.4 or later which contains the proper field validation fix.
Fix this in Drupal
Scoped from the published advisory
- Consultation3.0 h
- Implementation4.0 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 $2,880.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2017-6921 — 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-2017-6921 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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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