Описание
Craft CMS: Sensitive File Disclosure / Server-Side File Read
The dataUrl() Twig function is included in Craft’s Twig sandbox allowlist, allowing any control panel user granted the utility:system-messages permission to embed a file-reading payload into system email templates. When those emails are sent, the server reads the target file and returns its contents as a base64-encoded data URL embedded in the email body. The .env file, which typically contains the database password, CRAFT_SECURITY_KEY, and third-party API keys, passes all of Craft’s existing dataUrl() protection checks and is fully exfiltrated. Obtaining CRAFT_SECURITY_KEY enables an attacker to forge session tokens and escalate to full admin account takeover.
Details
Affected versions: Craft CMS 4.x, 5.x (confirmed against 5.9.19)
The vulnerability arises from the combination of three code facts:
-
dataUrl is in the Twig sandbox allowlist src/config/twig-sandbox.php, line 115: php'allowedFunctions' => [ ... 'dataUrl', // ← allows file reading inside sandboxed templates ... ],
-
Html::dataUrl() does not block dotfiles src/helpers/Html.php, lines 1065–1090. The function applies four checks before reading a file:
Must be within the project root .env is at the root Must not be in a system directory (config/, vendor/, storage/, templates/) .env is not Must not be a .php file .env has no extension File must exist .env always exists in a Craft install
There is no check for dotfiles or specifically for .env. All four checks pass silently and file_get_contents() is called, with the result returned as data:text/plain;base64,....
- System message body is rendered via renderSandboxedString() src/mail/Mailer.php, lines 181–183: php$subject = $view->renderSandboxedString($systemMessage->subject, $variables); $textBody = $view->renderSandboxedString($systemMessage->body, $variables); $htmlBody = $view->renderSandboxedString($systemMessage->body, $variables, escapeHtml: true);
Any body content saved to a system message is executed inside the Twig sandbox when the email renders. Because dataUrl is in allowedFunctions, the sandbox policy permits its execution without restriction.
Access control: The utility:system-messages permission is a non-admin CP permission grantable to any user group via Settings > Users > Groups. It is not restricted to admins.
Impact
Vulnerability type: Sensitive File Disclosure / Server-Side File Read Who is impacted: Any Craft CMS 4.x or 5.x installation where at least one non-admin control panel user has been granted the utility:system-messages permission, and email sending is configured.
Resources:
Пакеты
craftcms/cms
>= 4.0.0-RC1, < 4.18.0
4.18.0
craftcms/cms
>= 5.0.0-RC1, < 5.10.0
5.10.0
Связанные уязвимости
Craft CMS is a content management system (CMS). In versions starting from 4.0.0-RC1 and prior to 4.18.0, and 5.0.0-RC1 and above, prior to 5.10.0, the dataUrl() Twig function is included in Craft’s Twig sandbox allowlist, allowing any control panel user granted the utility:system-messages permission to embed a file-reading payload into system email templates. When those emails are sent, the server reads the target file and returns its contents as a base64-encoded data URL embedded in the email body. The .env file, which typically contains the database password, CRAFT_SECURITY_KEY, and third-party API keys, passes all of Craft’s existing dataUrl() protection checks and is fully exfiltrated. Obtaining CRAFT_SECURITY_KEY enables an attacker to forge session tokens and escalate to full admin account takeover. This issue has been fixed in versions 4.18.0 and 5.10.0.