CVE-2026-42845 Grav: Anonymous Page Content Overwrite via Form File Upload filename Override
An attacker can overwrite page content via file upload in the Grav form plugin, potentially escalating privileges to super-admin.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-42845?
CVE-2026-42845 is a high-severity vulnerability in getgrav grav-plugin-form, published on 11 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
The form plugin for Grav adds the ability to create and use forms. Prior to 9.1.0 , there is an unauthenticated page-content overwrite via file upload (GHSA-w4rc-p66m-x6qq). Public form uploads now strip path components from the POST-supplied filename and hard-block page-content extensions (`md`, `yaml`, `yml`, `json`, `twig`, `ini`) regardless of the configurable dangerous-extensions list. A permissive `accept` policy combined with the default `destination: self@` could otherwise let an attacker overwrite the page's own `.md` and pivot to super-admin via a `process: save` action. This vulnerability is fixed in 9.1.0.
Weakness: CWE-73
Which versions are affected by CVE-2026-42845?
2 open source packages ship an affected version, including getgrav/grav-plugin-form.
| Package | Affected | Fixed in |
|---|---|---|
getgrav/grav-plugin-form Packagist | All versions | 9.1.0 |
getgrav/grav-plugin-form Packagist | All versions | 9.1.0 |
How do I fix CVE-2026-42845?
Upgrade getgrav/grav-plugin-form to 9.1.0 or later.
Is CVE-2026-42845 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42845 exists.
Sources
Also known as GHSA-w4rc-p66m-x6qq.