Twig Sandbox Escape by authenticated users with access to editing CMS templates when safemode is enabled.

Impact

An authenticated backend user with the cms.manage_pages, cms.manage_layouts, or cms.manage_partials permissions who would normally not be permitted to provide PHP code to be executed by the CMS due to cms.enableSafeMode being enabled is able to write specific Twig code to escape the Twig sandbox and execute arbitrary PHP.

This is not a problem for anyone that trusts their users with those permissions to normally write & manage PHP within the CMS by not having cms.enableSafeMode enabled, but would be a problem for anyone relying on cms.enableSafeMode to ensure that users with those permissions in production do not have access to write & execute arbitrary PHP.

Patches

Issue has been patched in Build 469 (v1.0.469) and v1.1.0.

Workarounds

Apply https://github.com/octobercms/october/compare/106daa2930de4cebb18732732d47d4056f01dd5b...7cb148c1677373ac30ccfd3069d18098e403e1ca to your installation manually if unable to upgrade to Build 469.

References

Reported by ka1n4t

For more information

If you have any questions or comments about this advisory:

• Email us at [email protected]

Threat assessment:

<img width=“1108” alt=“Screen Shot 2020-10-10 at 1 21 13 PM” src=“https://user-images.githubusercontent.com/7253840/95663316-7de28b80-0afb-11eb-999d-a6526cf78709.png”>