GHSA-f5wm-88jv-g5hxHigh▾ TwilightCraft CMS: Authenticated RCE through Twig sandbox escape
▾ Twilight zone — High severity, or a signal on a lesser flaw
impact 41.3 · likelihood 0 · exploitation 0
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The Twig sandbox mechanism in Craft CMS is configured to allow dangerous functionality from the Yii framework, leading to authenticated RCE in a manner similar to previously disclosed vulnerabilities.
The Twig sandbox in Craft CMS works by implementing Twig's SecurityPolicyInterface. The resulting SecurityPolicy class implements the checkMethodAllowed and checkPropertyAllowed methods of the interface. The implementations compare whether the called method or property is in a configured allowlist or is marked with the AllowedInSandbox attribute.
Additionally, SecurityPolicy allows the allowlisting of whole classes, which is shorthand for allowing all methods and properties of that class to be called. Both the allowlists for tags, filters, variables, methods, properties, and classes, as well as the AllowedInSandbox attribute mechanism, are preconfigured by Craft CMS to allow user-defined templates to use core functionality unimpeded. Additionally, Craft CMS project developers can add more to the allowlists or mark their custom methods and so on as safe with AllowedInSandbox.
The SecurityPolicy class's allowlisting mechanism is potentially dangerous, as it allows all methods and properties on an object of the allowed class. This means that the checked object can be a subclass and be allowed. And it means that the allowed methods and properties can be defined on any class of the class hierarchy of the object, which does not have to be the allowed class itself.
Craft CMS uses the AllowedInSandbox attribute to mark the ElementInterface as safe. The Element class implements this interface and is the base class for many relevant model classes in Craft CMS, like Entry, User, Asset and so on. Additionally, Element extends the craft\base\Component class. Going up the class hierarchy of craft\base\Component, eventually the class yii\base\Component is reached, which is located in the Yii framework used by CraftCMS. yii\base\Component is known to contain a dangerous arbitrary function call gadget which leads to previously disclosed RCE vulnerabilities in Craft CMS (GHSA-255j-qw47-wjh5, GHSA-2fph-6v5w-89hh, GHSA-7jx7-3846-m7w7, GHSA-qrgm-p9w5-rrfw). Due to lax class allowlisting, this function-call gadget is allowed in the Twig sandbox. This allows sandboxed Twig templates to use known payloads based on the function-call gadget to achieve RCE.
An authenticated attacker with permission to access the control panel can render a malicious Twig template and gain RCE, even if the Twig sandbox is enabled through enableTwigSandbox().
craftcms/cms >= 5.0.0-RC1, < 5.10.7craftcms/cms >= 4.0.0-RC1, < 4.18.3Upgrade to a patched release:
craftcms/cms 5.10.7craftcms/cms 4.18.3Connected by shared product, vendor, weakness, or advisory.
GHSA-xxpx-f366-4xpqMediumCraft CMS:Authorization bypass: view-only Categories user can modify category structure via structures/move-element
GHSA-wg23-69c2-gjc8CriticalCraft CMS: Passkey login accepts replayed WebAuthn assertions
GHSA-p8x7-9vfw-p7vcHighCraft CMS: Arbitrary user password reset leading to administrator account takeover
GHSA-2rp4-x2j7-qmccMediumCraft CMS: Stored XSS in the control panel via unescaped draft name
GHSA-7hxc-f267-h5q7LowCraft CMS: Incorrect path validation could potentially lead to path traversal
GHSA-rvmm-v933-jgxqMediumCraft CMS: Missing authorization check allows non-admin control panel users access to user registration metrics