Impact Python's "format" functionality allows someone controlling the format string to "read" objects accessible (recursively) via attribute access and subscription from accessible objects. Those attribute accesses and subscriptions use Python's full blown getattr and getitem, not the policy restricted AccessControl variants getattr and getitem. This can lead to critical information disclosure.

AccessControl already provides a safe variant for str.format and denies access to string.Formatter. However, str.formatmap is still unsafe.

Affected are all users who allow untrusted users to create AccessControl controlled Python code and execute it.

Patches A fix will be introduced in the versions 4.4, 5.8 and 6.2.

Workarounds There are no workarounds.

References https://github.com/zopefoundation/RestrictedPython/security/advisories/GHSA-xjw2-6jm9-rf67 describes the corresponding problem for RestrictedPython.

Impact Background: The optional add-on package Products.PythonScripts adds Script (Python) to the list of content items a user can add to the Zope object database. Inside these scripts users can write Python code that is executed when rendered through the web. The code environment in these script objects is limited, it relies on the RestrictedPython package to provide a "safe" subset of Python instructions as well as the AccessControl package that defines security policies for execution in the context of a Zope application.

Recently the AccessControl package was updated to fix a remote code execution security issue. A link to the security advisory is provided in the References section below. The bug tightens the AccessControl security policies for Zope by blocking access to unsafe classes inside the Python string module.

You are only affected if the following are true:

- You use Python 3 for your Zope deployment (Zope 4 on Python 2 is not affected) - You run Zope 4 below version 4.6.3 or Zope 5 below version 5.3 - You have installed the optional Products.PythonScripts add-on package

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 versions 4.3 and 5.2. Zope releases 4.6.3 and 5.3 now require these new AccessControl releases.

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.

References AccessControl security advisory GHSA-qcx9-j53g-ccgf

For more information If you have any questions or comments about this advisory: Open an issue in the Zope issue tracker Email us at security@plone.org

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 Email us at security@plone.org