Improper access control in Form plugin for Grav CMS - CVE-2026-42845
Published: May 5, 2026 / Updated: May 20, 2026
Vulnerability identifier: #VU130090
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-42845
CWE-ID: CWE-284
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to escalate privileges.
The vulnerability exists due to improper access control in the Form plugin file upload handler and page content file handling when processing file uploads with a POST-supplied filename override. A remote attacker can upload a specially crafted markdown file with a chosen filename to overwrite a page's .md content file and escalate privileges.
Exploitation requires a form upload field that permits text files, such as using accept: ['*'], with uploads directed to the page directory via the default self@ destination.
Affected software
Form plugin for Grav CMS
How to mitigate CVE-2026-42845
Install security update from vendor's website.
Form plugin for Grav CMS - update to 9.1.0