CVE-2021-33509: Plone Remote Code Execution Vulnerability

CRITICAL
Advisory Identifier: GHSA-hm2p-fhwx-9285
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CVSS 9.9
CWE-732
Published
Advisory Summary

CVE-2021-33509 is a CRITICAL (CVSS 9.9) remote code execution vulnerability (CWE-732: Incorrect Permission Assignment for Critical Resource) affecting Plone libraries in the PyPI ecosystem. The issue involves incorrect permission assignment for critical resource in plone. Remediation is available by upgrading affected packages to version 5.2.5.

CVE-2021-33509 at a Glance

CVE Identifier CVE-2021-33509
GHSA Identifier GHSA-hm2p-fhwx-9285
Severity CRITICAL
CVSS v3.1 Base Score 9.9
CWE Classification CWE-732: Incorrect Permission Assignment for Critical Resource
Affected Product Plone
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 9.9

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Changed (S:C)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2021-33509

To remediate this vulnerability, upgrade all affected Plone dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

Plone fixed: 5.2.5 
pip install Plone>=5.2.5
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show Plone

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2021-33509, inspect your installed packages using pip:

pip show Plone

Analyze the terminal output to locate any version of Plone in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 5.2.5), your application is affected.

Note: The pip show Plone command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-732: Incorrect Permission Assignment for Critical Resource, where the product specifies permissions for a security-critical resource in a way that allows that resource to be read or modified by unintended actors. In Plone, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

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.

CVE-2021-33509 Affected Plone Versions

1 component(s)
Fixed Versions:
5.2.5
Product / Package Ecosystem Affected Versions Fixed Version
Plone
pypi/Plone
PyPI
< 5.2.5
5.2.5

References

NVD — CVE-2021-33509 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-33509
GitHub Advisory / Wiki ADVISORY
https://github.com/advisories/GHSA-hm2p-fhwx-9285
Plone Source Repository REPOSITORY
https://github.com/plone/Plone
Plone Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/plone/PYSEC-2021-81.yaml
Plone Security Information SECURITY
https://plone.org/security/hotfix/20210518/writing-arbitrary-files-via-docutils-and-python-script
Plone Security Information SECURITY
http://www.openwall.com/lists/oss-security/2021/05/22/1

Frequently Asked Questions

What is CVE-2021-33509?
CVE-2021-33509 is a security vulnerability in Plone involving Incorrect Permission Assignment for Critical Resource in Plone under CWE-732: Incorrect Permission Assignment for Critical Resource.
Which Plone versions are affected?
Affected versions include releases prior to 5.2.5 across affected packages: Plone.
What version fixes CVE-2021-33509?
Upgrading to 5.2.5 (or the latest patched release for your respective branch) resolves the vulnerability.
Is Plone affected?
Yes, Plone is affected in releases prior to 5.2.5. Upgrade your dependency to 5.2.5 or later.
What is the CVSS score of CVE-2021-33509?
CVE-2021-33509 has a CVSS v3.1 base score of 9.9 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H.
What CWE is associated with CVE-2021-33509?
CVE-2021-33509 is classified under CWE-732: Incorrect Permission Assignment for Critical Resource (The product specifies permissions for a security-critical resource in a way that allows that resource to be read or modified by unintended actors.).
How can I check PyPI dependencies for CVE-2021-33509?
Run the dependency tree command: 'pip show Plone'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-hm2p-fhwx-9285",
  "modified" : "2024-10-18T21:49:59Z",
  "published" : "2021-06-15T16:11:38Z",
  "aliases" : [ "CVE-2021-33509" ],
  "summary" : "Incorrect Permission Assignment for Critical Resource\tin Plone",
  "details" : "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.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "Plone"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "5.2.5"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-33509"
  }, {
    "type" : "ADVISORY",
    "url" : "https://github.com/advisories/GHSA-hm2p-fhwx-9285"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/plone/Plone"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/plone/PYSEC-2021-81.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://plone.org/security/hotfix/20210518/writing-arbitrary-files-via-docutils-and-python-script"
  }, {
    "type" : "WEB",
    "url" : "http://www.openwall.com/lists/oss-security/2021/05/22/1"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-732" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-05-27T21:32:19Z",
    "nvd_published_at" : "2021-05-21T22:15:00Z"
  }
}