Grav has Broken Access Control which allows an Editor to modify the page's YAML Frontmatter to alter form processing actions
The advisory, in context
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
-
Have Admin and Form plugins installed
-
Connect to panel as admin, create user and give him permission for pages all
-
Now connect as that user and notice you cant edit any process field in the panel
-
Change anything in the content of the form and save
-
Intercept the request:
-
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 packages
Start with the recorded fix for your release branch. Check your installed version and test compatibility before upgrading. Fixing this advisory does not rule out other vulnerabilities in the release.
Earlier releases before 1.8.0-beta.27
Fixed in 1.8.0-beta.27
317 explicitly affected versions
0.8.0, 0.9.0, 0.9.1, 0.9.10, 0.9.11, 0.9.12, 0.9.13, 0.9.14, 0.9.15, 0.9.16, 0.9.17, 0.9.18, 0.9.19, 0.9.2, 0.9.20, 0.9.21, 0.9.22, 0.9.23, 0.9.24, 0.9.25, 0.9.26, 0.9.27, 0.9.28, 0.9.29, 0.9.3, 0.9.30, 0.9.31, 0.9.32, 0.9.33, 0.9.34, 0.9.35, 0.9.36, 0.9.37, 0.9.38, 0.9.39, 0.9.4, 0.9.40, 0.9.41, 0.9.42, 0.9.43, 0.9.44, 0.9.45, 0.9.5, 0.9.6, 0.9.7, 0.9.8, 0.9.9, 1.0.0, 1.0.0-rc.1, 1.0.0-rc.2, 1.0.0-rc.3, 1.0.0-rc.4, 1.0.0-rc.5, 1.0.0-rc.6, 1.0.1, 1.0.10, 1.0.2, 1.0.3, 1.0.4, 1.0.5, 1.0.6, 1.0.7, 1.0.8, 1.0.9, 1.1.0, 1.1.0-beta.1, 1.1.0-beta.2, 1.1.0-beta.3, 1.1.0-beta.4, 1.1.0-beta.5, 1.1.0-rc.1, 1.1.0-rc.2, 1.1.0-rc.3, 1.1.1, 1.1.10, 1.1.11, 1.1.12, 1.1.13, 1.1.14, 1.1.15, 1.1.16, 1.1.17, 1.1.2, 1.1.3, 1.1.4, 1.1.5, 1.1.6, 1.1.7, 1.1.8, 1.1.9, 1.1.9-rc.1, 1.1.9-rc.2, 1.1.9-rc.3, 1.2.0, 1.2.0-rc.1, 1.2.0-rc.2, 1.2.0-rc.3, 1.2.1, 1.2.2, 1.2.3, 1.2.4, 1.3.0, 1.3.0-rc.1, 1.3.0-rc.2, 1.3.0-rc.3, 1.3.0-rc.4, 1.3.0-rc.5, 1.3.1, 1.3.10, 1.3.2, 1.3.3, 1.3.4, 1.3.5, 1.3.6, 1.3.7, 1.3.8, 1.3.9, 1.4.0, 1.4.0-beta.1, 1.4.0-beta.2, 1.4.0-beta.3, 1.4.0-rc.1, 1.4.0-rc.2, 1.4.1, 1.4.2, 1.4.3, 1.4.4, 1.4.5, 1.4.6, 1.4.7, 1.4.8, 1.5.0, 1.5.0-beta.1, 1.5.0-beta.2, 1.5.0-rc.1, 1.5.1, 1.5.10, 1.5.2, 1.5.3, 1.5.4, 1.5.5, 1.5.6, 1.5.7, 1.5.8, 1.5.9, 1.6.0, 1.6.0-beta.1, 1.6.0-beta.2, 1.6.0-beta.3, 1.6.0-beta.4, 1.6.0-beta.5, 1.6.0-beta.6, 1.6.0-beta.7, 1.6.0-beta.8, 1.6.0-rc.1, 1.6.0-rc.2, 1.6.0-rc.3, 1.6.0-rc.4, 1.6.1, 1.6.10, 1.6.11, 1.6.12, 1.6.13, 1.6.14, 1.6.15, 1.6.16, 1.6.17, 1.6.18, 1.6.19, 1.6.2, 1.6.20, 1.6.21, 1.6.22, 1.6.23, 1.6.24, 1.6.25, 1.6.26, 1.6.27, 1.6.28, 1.6.29, 1.6.3, 1.6.30, 1.6.31, 1.6.4, 1.6.5, 1.6.6, 1.6.7, 1.6.8, 1.6.9, 1.7.0, 1.7.0-beta.1, 1.7.0-beta.10, 1.7.0-beta.2, 1.7.0-beta.3, 1.7.0-beta.4, 1.7.0-beta.5, 1.7.0-beta.6, 1.7.0-beta.7, 1.7.0-beta.8, 1.7.0-beta.9, 1.7.0-rc.1, 1.7.0-rc.10, 1.7.0-rc.11, 1.7.0-rc.12, 1.7.0-rc.13, 1.7.0-rc.14, 1.7.0-rc.15, 1.7.0-rc.16, 1.7.0-rc.17, 1.7.0-rc.18, 1.7.0-rc.19, 1.7.0-rc.2, 1.7.0-rc.20, 1.7.0-rc.3, 1.7.0-rc.4, 1.7.0-rc.5, 1.7.0-rc.6, 1.7.0-rc.7, 1.7.0-rc.8, 1.7.0-rc.9, 1.7.1, 1.7.10, 1.7.12, 1.7.13, 1.7.14, 1.7.15, 1.7.16, 1.7.17, 1.7.18, 1.7.19, 1.7.20, 1.7.21, 1.7.22, 1.7.23, 1.7.24, 1.7.25, 1.7.26, 1.7.26.1, 1.7.27, 1.7.27.1, 1.7.28, 1.7.29, 1.7.29.1, 1.7.3, 1.7.30, 1.7.31, 1.7.32, 1.7.33, 1.7.34, 1.7.35, 1.7.36, 1.7.37, 1.7.37.1, 1.7.38, 1.7.39, 1.7.39.1, 1.7.39.2, 1.7.39.3, 1.7.39.4, 1.7.4, 1.7.40, 1.7.41, 1.7.41.1, 1.7.41.2, 1.7.42, 1.7.42.1, 1.7.42.2, 1.7.42.3, 1.7.43, 1.7.44, 1.7.45, 1.7.46, 1.7.47, 1.7.48, 1.7.49, 1.7.49.1, 1.7.49.2, 1.7.49.3, 1.7.49.4, 1.7.49.5, 1.7.5, 1.7.51, 1.7.52, 1.7.53, 1.7.53.1, 1.7.53.2, 1.7.53.3, 1.7.6, 1.7.7, 1.7.8, 1.7.9, 1.8.0-beta.1, 1.8.0-beta.10, 1.8.0-beta.11, 1.8.0-beta.12, 1.8.0-beta.13, 1.8.0-beta.14, 1.8.0-beta.15, 1.8.0-beta.16, 1.8.0-beta.17, 1.8.0-beta.18, 1.8.0-beta.19, 1.8.0-beta.2, 1.8.0-beta.20, 1.8.0-beta.21, 1.8.0-beta.22, 1.8.0-beta.23, 1.8.0-beta.24, 1.8.0-beta.25, 1.8.0-beta.26, 1.8.0-beta.3, 1.8.0-beta.4, 1.8.0-beta.5, 1.8.0-beta.6, 1.8.0-beta.7, 1.8.0-beta.8, 1.8.0-beta.9
View affected-version evidence
{
"ranges": [
{
"events": [
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{
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}
],
"type": "ECOSYSTEM"
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