GHSA-MC5Q-6HPJ-RP7J

Vulnerability from github – Published: 2026-09-02 21:41 – Updated: 2026-09-02 21:41
VLAI
Summary
Grav: Twig sandbox config exfiltration via grav.offsetGet + dump filter (CVE-2026-44738 bypass)
Details

Summary

The Twig content sandbox replaces config with the redacted SandboxConfig facade and strips Config::get/toArray from the method allowlist (GHSA-j274-39qw-32c9), so editor content can't read config secrets via config. That's bypassable: grav is the raw container, offsetget is allow-listed on it, so grav.offsetGet('config') returns the real Config. The allow-listed filters json_encode/print_r/yaml_encode then serialize it at the PHP level, never hitting the sandbox method gate, dumping the whole config tree including every plugins.* secret (SMTP creds, API keys, plugin DB creds). Incomplete fix for GHSA-j274-39qw-32c9. security.salt does not leak (it lives outside config).

Details

The documented path is blocked: config is the SandboxConfig facade (Twig.php:660) and the raw Config/Data method entries are stripped when config_access is false, so {{ config.get(...) }} returns the default and {{ grav.offsetGet('config').get(...) }} raises SecurityNotAllowedMethodError.

The bypass uses two allow-listed primitives the redaction doesn't cover:

  1. grav.offsetGet('config') returns the raw Config. The SandboxConfig facade replaces only the config variable, not grav['config']; offsetget is allow-listed on Grav\Common\Grav in system/config/security.yaml.
  2. json_encode/print_r/yaml_encode serialize the object inside the filter and never call GravSecurityPolicy::checkMethodAllowed (GravSecurityPolicy.php:65), so the stripped methods don't matter.

Bug class: object-dumping filters bypass the sandbox member gate. The same dump reaches page/pages/uri/user via their allow-listed accessors; config is the secret-bearing target.

Reachable below the publisher-Twig opt-in: a _-prefixed slug is modular (Page.php:228), and Page::content() sets $process_twig = $scan_twig_xss || $this->modularTwig() (Page.php:816), so a modular child's body Twig is sandboxed-rendered even with twig_content.process_enabled false (the default), while $scan_twig_xss stays false so the render-time XSS scan (GHSA-2c4f-86xc-cr74) is skipped. Any admin.pages author (or filesystem write to user/pages) exfiltrates config on a stock install. On a regular process.twig page the whole-tree dump trips the XSS scan and is blanked, but a targeted split/slice extraction of one subtree is XSS-clean and survives.

PoC

Sandboxed render, config_access default false. First two lines show the gate holding, third is the bypass:

{{ config.get('plugins.email.mailer.smtp.password', 'DENIED') }}
{# => DENIED #}
{{ grav.offsetGet('config').get('plugins.email.mailer.smtp.password') }}
{# => SecurityNotAllowedMethodError 'get' #}
{{ grav.offsetGet('config')|json_encode }}
{# => {...,"plugins":{"email":{"mailer":{"smtp":{"password":"CANARY..."}}}},...} #}

Stock-install reproduction (no user/config/security.yaml):

# user/config/plugins/email.yaml  -- decoy secret
mailer: { smtp: { password: CANARY_SMTP_PW_8b3f1 } }
# user/pages/70.parent/default.md
---
title: Parent
content: { items: '@self.modular' }
template: modular
---
{# user/pages/70.parent/_secret/default.md #}
---
title: Secret
template: modular/text
---
{{ grav.offsetGet('config')|json_encode }}
curl -s http://localhost/parent   # body contains CANARY_SMTP_PW_8b3f1

logs/security.log shows no sandbox block and no XSS scan for the route. Verified on Grav 2.0.1 (6f619f0ae), PHP 8.4.22, Twig 3.26.1-DEV.

Impact

A page author (admin.pages, no admin/super) reads the entire config tree: plugin SMTP credentials, API keys, plugin DB credentials. Read-only. Default install; the modular path needs no Twig opt-in.

Fix

system/config/security.yaml: drop offsetget (and __get) from twig_sandbox.allowed_methods for Grav\Common\Grav -- the legit uses are theme/getversion; offsetget is the raw-container reach. Closes the demonstrated path.

Sandbox-wide: make json_encode/print_r/yaml_encode/string refuse non-allow-listed objects when $env->isSandboxed() (mirror the Closure-only guard Twig applies to map/filter/reduce). Closes the class for page/pages/uri/user too.

Show details on source website

{
  "affected": [
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "getgrav/grav"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.0.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-61842"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-200"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-02T21:41:12Z",
    "nvd_published_at": "2026-08-19T16:18:17Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nThe Twig content sandbox replaces `config` with the redacted `SandboxConfig` facade and strips `Config::get`/`toArray` from the method allowlist (GHSA-j274-39qw-32c9), so editor content can\u0027t read config secrets via `config`. That\u0027s bypassable: `grav` is the raw container, `offsetget` is allow-listed on it, so `grav.offsetGet(\u0027config\u0027)` returns the real `Config`. The allow-listed filters `json_encode`/`print_r`/`yaml_encode` then serialize it at the PHP level, never hitting the sandbox method gate, dumping the whole config tree including every `plugins.*` secret (SMTP creds, API keys, plugin DB creds). Incomplete fix for GHSA-j274-39qw-32c9. `security.salt` does not leak (it lives outside config).\n\n### Details\n\nThe documented path is blocked: `config` is the `SandboxConfig` facade (`Twig.php:660`) and the raw `Config`/`Data` method entries are stripped when `config_access` is false, so `{{ config.get(...) }}` returns the default and `{{ grav.offsetGet(\u0027config\u0027).get(...) }}` raises `SecurityNotAllowedMethodError`.\n\nThe bypass uses two allow-listed primitives the redaction doesn\u0027t cover:\n\n1. `grav.offsetGet(\u0027config\u0027)` returns the raw `Config`. The `SandboxConfig` facade replaces only the `config` variable, not `grav[\u0027config\u0027]`; `offsetget` is allow-listed on `Grav\\Common\\Grav` in `system/config/security.yaml`.\n2. `json_encode`/`print_r`/`yaml_encode` serialize the object inside the filter and never call `GravSecurityPolicy::checkMethodAllowed` (`GravSecurityPolicy.php:65`), so the stripped methods don\u0027t matter.\n\nBug class: object-dumping filters bypass the sandbox member gate. The same dump reaches `page`/`pages`/`uri`/`user` via their allow-listed accessors; `config` is the secret-bearing target.\n\nReachable below the publisher-Twig opt-in: a `_`-prefixed slug is modular (`Page.php:228`), and `Page::content()` sets `$process_twig = $scan_twig_xss || $this-\u003emodularTwig()` (`Page.php:816`), so a modular child\u0027s body Twig is sandboxed-rendered even with `twig_content.process_enabled` false (the default), while `$scan_twig_xss` stays false so the render-time XSS scan (GHSA-2c4f-86xc-cr74) is skipped. Any `admin.pages` author (or filesystem write to `user/pages`) exfiltrates config on a stock install. On a regular `process.twig` page the whole-tree dump trips the XSS scan and is blanked, but a targeted `split`/`slice` extraction of one subtree is XSS-clean and survives.\n\n### PoC\n\nSandboxed render, `config_access` default false. First two lines show the gate holding, third is the bypass:\n\n```twig\n{{ config.get(\u0027plugins.email.mailer.smtp.password\u0027, \u0027DENIED\u0027) }}\n{# =\u003e DENIED #}\n{{ grav.offsetGet(\u0027config\u0027).get(\u0027plugins.email.mailer.smtp.password\u0027) }}\n{# =\u003e SecurityNotAllowedMethodError \u0027get\u0027 #}\n{{ grav.offsetGet(\u0027config\u0027)|json_encode }}\n{# =\u003e {...,\"plugins\":{\"email\":{\"mailer\":{\"smtp\":{\"password\":\"CANARY...\"}}}},...} #}\n```\n\nStock-install reproduction (no `user/config/security.yaml`):\n\n```yaml\n# user/config/plugins/email.yaml  -- decoy secret\nmailer: { smtp: { password: CANARY_SMTP_PW_8b3f1 } }\n```\n\n```\n# user/pages/70.parent/default.md\n---\ntitle: Parent\ncontent: { items: \u0027@self.modular\u0027 }\ntemplate: modular\n---\n```\n\n```twig\n{# user/pages/70.parent/_secret/default.md #}\n---\ntitle: Secret\ntemplate: modular/text\n---\n{{ grav.offsetGet(\u0027config\u0027)|json_encode }}\n```\n\n```bash\ncurl -s http://localhost/parent   # body contains CANARY_SMTP_PW_8b3f1\n```\n\n`logs/security.log` shows no sandbox block and no XSS scan for the route. Verified on Grav 2.0.1 (6f619f0ae), PHP 8.4.22, Twig 3.26.1-DEV.\n\n### Impact\n\nA page author (`admin.pages`, no admin/super) reads the entire config tree: plugin SMTP credentials, API keys, plugin DB credentials. Read-only. Default install; the modular path needs no Twig opt-in.\n\n### Fix\n\n`system/config/security.yaml`: drop `offsetget` (and `__get`) from `twig_sandbox.allowed_methods` for `Grav\\Common\\Grav` -- the legit uses are `theme`/`getversion`; `offsetget` is the raw-container reach. Closes the demonstrated path.\n\nSandbox-wide: make `json_encode`/`print_r`/`yaml_encode`/`string` refuse non-allow-listed objects when `$env-\u003eisSandboxed()` (mirror the Closure-only guard Twig applies to `map`/`filter`/`reduce`). Closes the class for `page`/`pages`/`uri`/`user` too.",
  "id": "GHSA-mc5q-6hpj-rp7j",
  "modified": "2026-09-02T21:41:13Z",
  "published": "2026-09-02T21:41:12Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/getgrav/grav/security/advisories/GHSA-mc5q-6hpj-rp7j"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-61842"
    },
    {
      "type": "WEB",
      "url": "https://github.com/getgrav/grav/commit/7efe70574e4cf01a251318478c13673029e93eb6"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/getgrav/grav"
    },
    {
      "type": "WEB",
      "url": "https://github.com/getgrav/grav/releases/tag/2.0.2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Grav: Twig sandbox config exfiltration via grav.offsetGet + dump filter (CVE-2026-44738 bypass)"
}



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