CVE-2021-32674: Remote Code Execution via traversal in TAL expressions
This advisory extends the previous advisory at https://github.com/zopefoundation/Zope/security/advisories/GHSA-5pr9-v234-jw36 with additional cases of TAL expression traversal vulnerabilities.
Impact Most Python modules are not available for using in TAL expressions that you can add through-the-web, for example in Zope Page Templates. This restriction avoids file system access, for example via the 'os' module. But some of the untrusted modules are available indirectly through Python modules that are available for direct use.
By default, you need to have the Manager role to add or edit Zope Page Templates through the web. Only sites that allow untrusted users to add/edit Zope Page Templates through the web are at risk.
Patches The problem has been fixed in Zope 5.21 and 4.6.1.
Workarounds The workaround is the same as for https://github.com/zopefoundation/Zope/security/advisories/GHSA-5pr9-v234-jw36: A site administrator can restrict adding/editing Zope Page Templates through the web using the standard Zope user/role permission mechanisms. Untrusted users should not be assigned the Zope Manager role and adding/editing Zope Page Templates through the web should be restricted to trusted users only.
References The previous advisory (GHSA-5pr9-v234-jw36)
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
Other sources
Zope is an open-source web application server. This advisory extends the previous advisory at https://github.com/zopefoundation/Zope/security/advisories/GHSA-5pr9-v234-jw36 with additional cases of TAL expression traversal vulnerabilities. Most Python modules are not available for using in TAL expressions that you can add through-the-web, for example in Zope Page Templates. This restriction avoids file system access, for example via the 'os' module. But some of the untrusted modules are available indirectly through Python modules that are available for direct use. By default, you need to have the Manager role to add or edit Zope Page Templates through the web. Only sites that allow untrusted users to add/edit Zope Page Templates through the web are at risk. The problem has been fixed in Zope 5.2.1 and 4.6.1. The workaround is the same as for https://github.com/zopefoundation/Zope/security/advisories/GHSA-5pr9-v234-jw36: A site administrator can restrict adding/editing Zope Page Templates through the web using the standard Zope user/role permission mechanisms. Untrusted users should not be assigned the Zope Manager role and adding/editing Zope Page Templates through the web should be restricted to trusted users only.
— MITRE
Affected Software
Remediation
Event History
Frequently Asked Questions
What is CVE-2021-32674?
CVE-2021-32674 is a vulnerability involving TAL expression traversal in Zope web application server.
What is the severity of CVE-2021-32674?
CVE-2021-32674 has a severity rating of 8.8 (high).
How does CVE-2021-32674 affect Zope servers?
CVE-2021-32674 affects Zope servers running versions up to 4.6.1 and versions between 5.0.0 and 5.2.1.
How can I fix CVE-2021-32674?
To fix CVE-2021-32674, update Zope to a version that includes the necessary security patches.
What is the CWE classification of CVE-2021-32674?
CVE-2021-32674 is classified as CWE-22 (Improper Limitation of a Pathname to a Restricted Directory).