Grav has Broken Access Control which allows an Editor to modify the page's YAML Frontmatter to alter form processing actions
Summary
Due to a broken access control vulnerability in the /admin/pages/{page_name} endpoint, an editor ( user with full permissions to pages ) can change the functionality of a form after submission.
Details
Due to improper authorization checks when modifying critical fields on a POST request to /admin/pages/{page_name}, an editor with only permissions to change basic content on the form is now able to change the functioning of the form through modifying the content of the data[_json][header][form] which is the YAML frontmatter which includes the process section which dictates what happens after a user submits the form which include some important actions that could lead to further vulnerabilities.
PoC
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Have Admin and Form plugins installed
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Connect to panel as admin, create user and give him permission for pages all
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Now connect as that user and notice you cant edit any process field in the panel
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Change anything in the content of the form and save
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Intercept the request:
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Now modify the field `data[_json][header][form] with the following payload URL-encoded not like this:
{"name":"ssti-test 2","fields":{"name":{"type":"text","label":"Name","required":true}},"buttons":{"submit":{"type":"submit","value":"Submit"}},"process":[{"message":"{{ evaluate_twig(form.value('name')) }}"}]}- Change the field and forward it:
Request goes through and changes have been made to the form.
Impact
- Attacker can modify submission logic of the form which leads to changing redirect value, email sending, changing template, breaking out of the Twig sandbox potentially executing code...
Fix recommendation
- Implement proper authorization checks to such requests especially when it contains fields user shouldn't be able to modify based on his role.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Composer package | getgrav/grav | < 1.8.0-beta.27 | 1.8.0-beta.27 |
References
- CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N- Weakness (CWE)
CWE-285- Platform
- Composer
- Package
getgrav/grav- Disclosed
- 02.12.2025
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-v8x2-fjv7-8hjh - CC BY 4.0
Vulnerability history: getgrav/grav
All published vulnerabilities of this package (Composer package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 99
- First → latest
- 11.2019 09.2026
- Without a fix
- 6
- Exploited in attacks
- 0
Severity breakdown
- Critical 7
- High 47
- Medium 41
- Low 4
Disclosures per year
- 2019: 1
- 2020: 1
- 2021: 4
- 2022: 10
- 2023: 5
- 2024: 8
- 2025: 23
- 2026: 47
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Grav has Broken Access Control which allows an Editor to modify the page's YAML Frontmatter to alter form processing actions this entry
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