Statamic CMS Privilege Escalation via Antlers Sandbox Escape and Session Bypass

CVE-2026-27939 represents a complex chain of vulnerabilities within the Statamic CMS Control Panel, specifically affecting the mechanisms designed to protect sensitive administrative operations. Statamic employs an "Elevated Session" concept (often referred to as "sudo mode"), which requires authenticated users to re-enter their password before accessing high-risk areas such as user management, system configuration, or addon settings. This vulnerability effectively nullifies that protection.

The core of the issue lies in the Antlers template engine, Statamic's proprietary parser. Due to insufficient sandboxing, the engine allowed authenticated users to access the underlying Laravel application instance. This exposure permitted the extraction of sensitive environment variables, including the APP_KEY, and the execution of arbitrary methods on available objects. Additionally, logic flaws in the redirect handling of the RendersControlPanelExceptions trait allowed attackers to circumvent the elevation prompt entirely by manipulating HTTP headers.

While the vulnerability requires an authenticated session to exploit, the privilege level required is low. Any user with access to the Control Panel—such as an editor or author—could leverage these flaws to elevate their privileges to Super Admin, resulting in a complete takeover of the CMS and the underlying server.

The vulnerability is rooted in three distinct architectural failures: the exposure of the global configuration object in the template context, the lack of method allow-listing in the Antlers parser, and insecure redirect logic.

1. Antlers Configuration Leak

Statamic's Antlers engine was configured to pass the entire application configuration to the parsing context via config()->all(). In Laravel applications, this configuration array contains critical secrets, most notably the APP_KEY. This key is used for encryption and signing session cookies. By injecting a specific Antlers tag (e.g., {{ config:app:key }}), an attacker could force the parser to render this secret value into the HTML response, effectively leaking the cryptographic root of trust for the application.

2. Unrestricted Method Invocation

The Antlers parser failed to enforce strict boundaries on method execution within the template context. The engine allowed recursive evaluation where user-supplied input could invoke methods on accessible PHP objects. For instance, if a User model was accessible in the context, an attacker could craft a payload like {{ user:update(['super' => true]) }}. The lack of a strict allow-list for callable methods meant that standard Eloquent model methods were exposed to the templating layer.

3. Logic Flaws in Exception Handling

The RendersControlPanelExceptions trait, responsible for intercepting unauthorized requests and redirecting the user to the password verification form, relied on the Referer header and _redirect input parameters without adequate validation. This introduced an Open Redirect vulnerability (CWE-601) that could be chained to bypass the elevation check. By crafting a request that pointed the redirect destination to an external or manipulated internal URL, the logic determining whether a user was "elevated" could be short-circuited.

The following analysis illustrates the critical difference between the vulnerable and patched implementations of the Antlers context handling. The primary fix involved restricting what data is passed to the parser and implementing a strict blocklist for method calls.

Vulnerable Implementation (Conceptual)

In the vulnerable versions, the Antlers parser initialized its context by merging global configurations directly. This indiscriminate merging made the app configuration namespace available as a top-level variable.

// Vulnerable Context Initialization
public function getContext()
{
    // DANGEROUS: Merging all config values into the template scope
    return array_merge(
        $this->data,
        ['config' => config()->all()] // Leaks APP_KEY, DB_PASSWORD, etc.
    );
}

When this code runs, a user inputting {{ config:app:key }} results in the parser traversing the array and outputting the base64-encoded key.

Patched Implementation

The patch introduced in version 6.4.0 removes the global config merge and implements a strictly defined accessor for configuration values that filters out sensitive keys. It also introduces a Blocklist for method calls.

// Patched Context Initialization
public function getContext()
{
    // SAFE: Config is no longer dumped blindly
    $context = $this->data;
    
    // Config access is now mediated by a specific tag that filters keys
    // Attempting {{ config:app:key }} now returns null or an error
    return $context;
}
 
// Method Invocation Guard
public function callMethod($object, $method, $args)
{
    if (in_array($method, ['update', 'delete', 'save', 'forceDelete'])) {
         throw new AccessDeniedException("Method [$method] is blocked in Antlers.");
    }
    
    return $object->$method(...$args);
}

The fix fundamentally changes the trust model of the template engine. Instead of assuming the template author is a trusted developer, the engine now treats template content as potentially untrusted, specifically blocking state-mutating methods on Eloquent models.

Exploitation of CVE-2026-27939 typically follows a two-stage process: extraction of secrets followed by privilege escalation. The attacker requires a valid account with access to any field parsed by Antlers (e.g., a Page title, a Blueprints field, or a Globals field).

Stage 1: Exfiltrating the APP_KEY

The attacker navigates to a content editing screen in the Control Panel and injects the malicious Antlers tag into a text field.

<!-- Payload injected into a 'Title' or 'Content' field -->
APP_KEY_LEAK: {{ config:app:key }}

Upon saving or previewing the content, the server renders the template. The response will contain the base64-encoded APP_KEY. This key is the "skeleton key" for the Laravel framework.

Stage 2: Session Forgery (The "Golden Ticket")

With the APP_KEY, the attacker can decrypt their own session cookie, modify the serialized session data, and re-encrypt it. The goal is to modify the session attributes that control user identity and elevation status.

1. Capture Cookie: The attacker captures their current statamic_session cookie.
2. Decrypt: Using the leaked APP_KEY and Laravel's decryption logic, the attacker reveals the session payload.
3. Elevate: The attacker modifies the session payload, changing the user ID to that of the Super Admin (usually ID 1) or setting the statamic.cp.last_activity and statamic.cp.elevated timestamps to the current time, bypassing the sudo prompt.
4. Re-encrypt: The modified payload is encrypted and signed using the APP_KEY.
5. Replace: The attacker replaces their browser cookie with the forged one and refreshes the page.

The system now recognizes the attacker as a fully authenticated Super Admin with an active "Elevated Session," allowing unrestricted access to all system functions.

The impact of this vulnerability is critical, warranting its CVSS score of 8.8. The compromise affects all three pillars of the CIA triad (Confidentiality, Integrity, Availability).

Confidentiality

The immediate leak of the APP_KEY allows for the decryption of any encrypted data stored by the application that uses Laravel's default encryption facilities. Furthermore, gaining Super Admin access allows the attacker to export all user data, site content, and form submissions.

Integrity

With Super Admin privileges, an attacker can modify any aspect of the site. They can inject malicious JavaScript (XSS) into frontend templates to target site visitors, modify payment gateway configurations to steal funds, or alter content to spread disinformation. The ability to invoke update() methods via Antlers also allows for direct database manipulation without SQL injection.

Availability

An attacker can delete critical system files, wipe the database (via the Control Panel's utility section), or misconfigure the system to cause denial of service. Since Statamic is a flat-file CMS by default, an attacker could also wipe the content/ directory, effectively deleting the entire website's data permanently if backups are not immutable.

The only complete remediation is to upgrade the Statamic CMS core to a patched version. The patches introduce necessary boundaries within the Antlers engine and harden the Control Panel's authentication flows.

Official Patches

• Statamic v5.x: Update to the latest v5 patch release immediately.
• Statamic v6.x: Update to version 6.4.0 or higher.

Post-Exploitation Cleanup (Mandatory)

If you suspect this vulnerability has been exploited, simply patching the code is insufficient. Because the APP_KEY may have been compromised, you must rotate it immediately.

1. Generate a new key: Run php artisan key:generate on your production server.
2. Invalidate Sessions: Rotating the key will automatically invalidate all existing user sessions, forcing everyone to log in again. This flushes any forged cookies.
3. Audit Logs: Review storage/logs/ and any access logs for requests containing suspicious Referer headers or unusual access to the Control Panel from unknown IP addresses.
4. Verify User List: Check the users/ directory (or database) for any new accounts with super: true permissions that were not authorized.