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Remote Code Execution via traversal in TAL expressions

High
dataflake published GHSA-rpcg-f9q6-2mq6 Jun 8, 2021

Package

Zope

Affected versions

<5.2.1, <4.6.1

Patched versions

5.2.1, 4.6.1

Description

This advisory extends the previous advisory at 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 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

For more information

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Severity

High

CVE ID

CVE-2021-32674

Weaknesses

No CWEs