October CMS safe mode bypass using Twig sandbox escape

Impact

An authenticated backend user with the editor.cms_pages, editor.cms_layouts, or editor.cms_partials permissions who would normally not be permitted to provide PHP code to be executed by the CMS due to cms.safe_mode being enabled can write specific Twig code to escape the Twig sandbox and execute arbitrary PHP.

This is not a problem for anyone who trusts their users with those permissions to usually write and manage PHP within the CMS by not having cms.safe_mode enabled. Still, it would be a problem for anyone relying on cms.safe_mode to ensure that users with those permissions in production do not have access to write and execute arbitrary PHP.

Patches

This issue has been patched in v3.4.15.

Workarounds

As a workaround, remove the specified permissions from untrusted users.

References

Credits to:

• Vasiliy Bodrov

For more information

If you have any questions or comments about this advisory:

• Email us at [email protected]