How severe is CVE-2026-55792?

No CVSS score has been assigned to CVE-2026-55792 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-55792?

CVE-2026-55792 affects the following packages: craftcms/cms (Packagist), craftcms/cms (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2026-55792?

Update craftcms/cms to 4.18.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-55792 is resolved across your whole dependency graph.

How do I detect CVE-2026-55792 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for craftcms/cms, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-55792 if there is no patch (or I can't update yet)?

Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Is CVE-2026-55792 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-55792 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-55792?

CVE-2026-55792 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 33th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-55792?

CVE-2026-55792 is classified as Information Exposure (CWE-200). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-55792 published, and has it been updated?

CVE-2026-55792 was published on July 1, 2026 and was last updated on October 21, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘 Packagist

Not in CISA KEV

CVE-2026-55792 — cms

Fix: craftcms/cms#18559

CVE-2026-55792 is a Information Exposure vulnerability in craftcms/cms. A fix is available for craftcms/cms — see the affected versions and patch details below.

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

Also known asGHSA-287w-mxq6-x2cp

Published

Jul 1, 2026

Updated

Oct 21, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Oct 24, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-55792.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs33th percentile — riskier than 33% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

2 pkgs affected

🐘craftcms/cms🐘craftcms/cms

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

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:

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

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`craftcms/cms`	≥ 4.0.0-RC1&&< 4.18.0	4.18.0`composer require craftcms/cms:^4.18.0`
🐘Packagist	`craftcms/cms`	≥ 5.0.0-RC1&&< 5.10.0	5.10.0`composer require craftcms/cms:^5.10.0`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for craftcms/cms, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update craftcms/cms to 4.18.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-55792 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Frequently Asked Questions

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 at

O3 Security · Impact-Aware SCA

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