CVE-2026-55792

Summary

Craft CMS: Sensitive File Disclosure / Server-Side File Read

Severity

medium

EPSS

0.4% (p33)

CWE

CWE-200

Also known as

GHSA-287w-mxq6-x2cp

Published

2026-07-06

Updated

2026-07-06

Advisory details

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:

1. dataUrl is in the Twig sandbox allowlist src/config/twig-sandbox.php, line 115: php'allowedFunctions' => [ ... 'dataUrl', // ← allows file reading inside sandboxed templates ... ],

2. 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,....

3. 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:

• https://github.com/craftcms/cms/pull/18559

References

• https://github.com/advisories/GHSA-287w-mxq6-x2cp
• https://github.com/craftcms/cms/security/advisories/GHSA-287w-mxq6-x2cp
• https://nvd.nist.gov/vuln/detail/CVE-2026-55792
• https://github.com/craftcms/cms/pull/18559

Related advisories

• GHSA-x76w-8c62-48mg — medium · Packagist/craftcms/cms
• GHSA-wg23-69c2-gjc8 — critical · Packagist/craftcms/cms
• CVE-2026-28697 — critical · Packagist/craftcms/cms
• GHSA-p8x7-9vfw-p7vc — high · Packagist/craftcms/cms
• GHSA-f5wm-88jv-g5hx — high · Packagist/craftcms/cms
• GHSA-265m-7826-wjqm — high · Packagist/craftcms/cms
• GHSA-86vw-x4ww-x467 — high · Packagist/craftcms/cms
• CVE-2026-55794 — high · Packagist/craftcms/cms

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