Craft CMS allows any authenticated control panel user to submit an element-search condition whose…

Why it is Amber

• CVSS 8.8 high

References

• https://github.com/craftcms/cms
• https://github.com/craftcms/cms/releases/tag/5.11.2
• https://github.com/craftcms/cms/security/advisories/GHSA-v4q3-2g5g-wjj6
• https://www.hckrt.com/hacktivity/HCKRT-DRNL9W

Original description

Craft CMS allows any authenticated control panel user to submit an element-search condition whose element selector is evaluated as a sandboxed Twig object template. Craft’s allowed column filter delegates property lookup to Yii ArrayHelper, outside Twig’s SecurityPolicy. Repeated single-segment lookups therefore bypass the sandbox’s empty property/method allowlists. The vulnerable condition value is ultimately cast to an integer. That does not protect the secret: the template can return author ID 1 when a guessed key character is correct and an impossible ID otherwise. The JSON endpoint returns entries for the first case and an empty array for the second, forming a stable remote character oracle. After recovering GeneralConfig::securityKey, the same user can compute Craft’s generic HMAC wire format offline. Signed parameters such as redirect are then accepted and passed to unsandboxed View::renderObjectTemplate(), where Twig’s string-callable form can invoke native PHP callables. The regression proof uses the harmless substr() callback and observes abcdef becoming cdef; it does not execute an OS command.