dbcve.org
PloneApplication

CVE-2021-33509

CRITICAL · 9.9 CVSS v3.1 Published 2021-05-21
Fix available
A fix is available. Upgrade to after 5.2.4 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable Zero-click

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
Plone through 5.2.4 allows remote authenticated managers to perform disk I/O via crafted keyword arguments to the ReStructuredText transform in a Python script.

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

Plone CMS through version 5.2.4 contains a vulnerability in its ReStructuredText transform functionality where authenticated manager users can inject crafted keyword arguments to perform arbitrary disk I/O operations, potentially allowing read/write of sensitive files on the server filesystem.

MitigationUpgrade Plone to a version beyond 5.2.4 that contains the security patch, or implement input validation/sanitization on keyword arguments passed to the ReStructuredText transform to prevent path traversal and unauthorized file access.

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
PloneApplication
Affected:<= 5.2.4

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
Low
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/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 checks

Work through these to decide whether this CVE applies to you.

  1. Check installed Plone version
    Locate and inspect Plone's version file or use Plone's management interface to determine the exact version number. Common locations include the 'plone.app.versioning' setup or the 'versions.cfg' file in the buildout configuration.
    Affected if The installed version is 5.2.4 or any earlier version (e.g., 5.2.3, 5.2.2, 5.2.1, 5.2.0, 5.1.x, 5.0.x).
  2. Verify ReStructuredText transform is enabled
    Examine the portal_transforms configuration in the ZMI (Zope Management Interface) or check the site's enabled content transforms to confirm that the ReStructuredText transform is actively registered and available.
    Affected if The ReStructuredText transform is present and enabled in the site's transform chain.
  3. Confirm manager-level user accounts exist
    Access the Plone User and Group management interface or check the acl_users repository in the ZMI to identify whether any user accounts with Manager role are present.
    Affected if At least one user account with Manager role exists in the system.
  4. Check for recent ReStructuredText content creation
    Review the site database for content items that utilize the ReStructuredText format or look for recent modifications to existing ReStructuredText-based content through the portal_catalog or content history.
    Affected if Content using the ReStructuredText format has been created or modified on the site.

A user is affected if they run Plone version 5.2.4 or earlier, have the ReStructuredText transform enabled, and possess at least one authenticated manager account capable of accessing the ReStructuredText transform functionality.

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 a release after 5.2.4
Interim mitigation

Upgrade Plone to a version beyond 5.2.4 that contains the security patch, or implement input validation/sanitization on keyword arguments passed to the ReStructuredText transform to prevent path traversal and unauthorized file access.

Recommended fix High confidence

Plone 5.2.5 or later (latest stable 5.x release)

  1. 1. Back up your Plone database and file system before attempting any upgrade
  2. 2. Review upgrade documentation at https://docs.plone.org/manage/upgrading/index.html
  3. 3. Test the upgrade in a staging environment first
  4. 4. Ensure you have manager-level access to perform the upgrade
  5. 5. Upgrade Plone from version 5.2.4 or earlier to version 5.2.5 or later (latest stable release recommended)
  6. 6. After upgrade, verify the ReStructuredText transform no longer allows arbitrary disk I/O through Python scripts
  7. 7. Confirm manager permissions are properly scoped post-upgrade
Caveat Review migration notes for potential breaking changes between 5.2.4 and newer versions; test thoroughly in staging

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

Fix this in Plone Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing10.0 h
  • Review / QA6.0 h
34.0 hours of engineering $5,940
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $9,504.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2021-33509 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2021-33509 in production — separate from our analysis above.

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.

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