CVE-2021-32807 Remote Code Execution via unsafe classes in otherwise permitted modules
Attackers with Manager role can execute arbitrary code via unsafe classes in permitted modules, requiring non-default web editing permissions.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2021-32807?
CVE-2021-32807 is a medium-severity code injection vulnerability in zopefoundation AccessControl, published on 30 Jul 2021. An attacker needs administrator access to exploit it, with no action from the victim.
Official description
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. 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. As a workaround, 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.
Which versions are affected by CVE-2021-32807?
10 open source packages ship an affected version, including accesscontrol, AccessControl and zope. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
accesscontrol PyPI | From 4.0 | 4.3, 5.2 |
accesscontrol PyPI | From 4.0 | 4.3 |
accesscontrol PyPI | From 5.0 | 5.2 |
AccessControl PyPI | From 4.0 | 4.3 |
AccessControl PyPI | From 5.0 | 5.2 |
zope PyPI | From 4.0 | 4.3, 5.2 |
4 more packages
zope PyPI | From 4.0 | 4.3 |
zope PyPI | From 4.0 | 4.3 |
zope PyPI | From 5.0 | 5.2 |
zope PyPI | From 5.0 | 5.2 |
Products include Zope Accesscontrol.
How do I fix CVE-2021-32807?
Upgrade accesscontrol to a fixed version for your release line: 4.3 or 5.2.
Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.
Is CVE-2021-32807 being exploited?
There is no known exploitation of CVE-2021-32807 in the wild and no public exploit code.
Other vulnerabilities in zopefoundation AccessControl
Sources
Also known as GHSA-qcx9-j53g-ccgf, PYSEC-2021-335, PYSEC-2021-875.