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Security Advisories: MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLWc0Z3EtajRwMi1qOGZy

Remote Code Execution via Script (Python) objects under Python 3

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 [email protected]

Permalink: https://github.com/advisories/GHSA-g4gq-j4p2-j8fr
JSON: https://advisories.ecosyste.ms/api/v1/advisories/MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLWc0Z3EtajRwMi1qOGZy
Source: GitHub Advisory Database
Origin: Unspecified
Severity: High
Classification: General
Published: over 3 years ago
Updated: 3 months ago

CVSS Score: 7.5
CVSS vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Identifiers: GHSA-g4gq-j4p2-j8fr, CVE-2021-32811
References:

• https://github.com/zopefoundation/Zope/security/advisories/GHSA-g4gq-j4p2-j8fr
• https://github.com/zopefoundation/AccessControl/security/advisories/GHSA-qcx9-j53g-ccgf
• https://nvd.nist.gov/vuln/detail/CVE-2021-32811
• https://github.com/zopefoundation/Zope/commit/f72a18dda8e9bf2aedb46168761668464a4be988
• https://github.com/zopefoundation/Zope/commit/869f947e586517566509e0ccdd4d99b60704cc02
• https://github.com/pypa/advisory-database/tree/main/vulns/zope/PYSEC-2021-368.yaml
• https://github.com/advisories/GHSA-g4gq-j4p2-j8fr

Repository: https://github.com/zopefoundation/Zope
Blast Radius: 15.4

Affected Packages