---
id: CVE-2021-32807
aliases:
  - GHSA-qcx9-j53g-ccgf
  - CVE-2021-32811
  - GHSA-g4gq-j4p2-j8fr
  - PYSEC-2021-335
  - PYSEC-2021-368
  - PYSEC-2021-370
  - PYSEC-2021-875
title: Remote Code Execution via unsafe classes in otherwise permitted modules
summary: Remote Code Execution via unsafe classes in otherwise permitted modules
severity: medium
cvss: 4.4
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:H/A:N'
vendor: accesscontrol
product: accesscontrol
ecosystem: pip
affected:
  - 'accesscontrol >= 4.0, < 4.3'
  - 'accesscontrol >= 5.0, < 5.2'
  - 'zope >= 4.0, < 4.3'
  - 'zope >= 5.0, < 5.2'
patched:
  - accesscontrol 4.3
  - accesscontrol 5.2
  - zope 4.3
  - zope 5.2
published: '2021-08-05'
updated: '2026-07-08'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-qcx9-j53g-ccgf'
references:
  - url: >-
      https://github.com/zopefoundation/AccessControl/security/advisories/GHSA-qcx9-j53g-ccgf
  - url: >-
      https://github.com/zopefoundation/Zope/security/advisories/GHSA-g4gq-j4p2-j8fr
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2021-32807'
  - url: >-
      https://github.com/zopefoundation/AccessControl/commit/ae2dab0cc34e6dd1561c5b12d4a56cd140f87e1d
  - url: >-
      https://github.com/zopefoundation/AccessControl/commit/b42dd4badf803bb9fb71ac34cd9cb0c249262f2c
  - url: >-
      https://github.com/zopefoundation/Zope/commit/869f947e586517566509e0ccdd4d99b60704cc02
  - url: >-
      https://github.com/zopefoundation/Zope/commit/f72a18dda8e9bf2aedb46168761668464a4be988
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/accesscontrol/PYSEC-2021-335.yaml
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/accesscontrol/PYSEC-2021-370.yaml
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/zope/PYSEC-2021-368.yaml
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/zope/PYSEC-2021-875.yaml
  - url: 'https://github.com/zopefoundation/AccessControl'
  - url: >-
      https://github.com/zopefoundation/AccessControl/blob/master/CHANGES.rst#51-2021-07-30
tags:
  - osv
  - pip
epss: 0.02049
epssPercentile: 0.80407
ingestedAt: '2026-07-08T18:25:52.402Z'
---

## Overview

### Impact
The module `AccessControl` defines security policies for Python code used in restricted code within Zope applications. Restricted code is any code that resides in Zope's object database, such as the contents of `Script (Python)` objects. 

The policies defined in `AccessControl` severely restrict access to Python modules and only exempt a few that are deemed safe, such as Python's `string` module. However, full access to the `string` module also allows access to the class `Formatter`, which can be overridden and extended within `Script (Python)` in a way that provides access to other unsafe Python libraries. Those unsafe Python libraries can be used for remote code execution.

By default, you need to have the admin-level Zope "Manager" role to add or edit `Script (Python)` objects through the web. Only sites that allow untrusted users to add/edit these scripts through the web - which would be a very unusual configuration to begin with - are at risk.

### Patches
The problem has been fixed in AccessControl 4.3 and 5.2.
Only AccessControl versions 4 and 5 are vulnerable, and only on Python 3, not Python 2.7.

### Workarounds
A site administrator can restrict adding/editing `Script (Python)` objects through the web using the standard Zope user/role permission mechanisms. Untrusted users should not be assigned the Zope Manager role and adding/editing these scripts through the web should be restricted to trusted users only. This is the default configuration in Zope.

### For more information
If you have any questions or comments about this advisory:
* Open an issue in the [AccessControl issue tracker](https://github.com/zopefoundation/AccessControl/issues)
* Email us at [security@plone.org](mailto:security@plone.org)

## Affected packages

- `accesscontrol >= 4.0, < 4.3`
- `accesscontrol >= 5.0, < 5.2`
- `zope >= 4.0, < 4.3`
- `zope >= 5.0, < 5.2`

## Remediation

Upgrade to a patched release:

- `accesscontrol 4.3`
- `accesscontrol 5.2`
- `zope 4.3`
- `zope 5.2`