---
id: "CVE-2026-103039"
kind: "vulnerability"
aliases: ["CVE-2026-103039"]
title: "Gravity Forms: unauthenticated PHP object injection through post custom fields"
severity: "critical"
cvss: 9.8
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["gravity-forms", "package", "php", "self-hosted", "wordpress"]
not_affected_if: ["managed-hosting", "no-post-custom-field-list", "plugin-version-above-3.1.2"]
published_at: "2026-10-30T07:16:30+00:00"
first_seen_at: "2026-10-30T07:29:00+00:00"
updated_at: "2026-10-30T07:30:04+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-103039", "first_seen_at": "2026-10-30T07:29:00+00:00"}]
---

# Gravity Forms: unauthenticated PHP object injection through post custom fields

Gravity Forms up to and including 3.1.2 passes a submitted post custom field value to WordPress's unrestricted maybe_unserialize(), letting an unauthenticated attacker inject a PHP object into post meta. The plugin has no gadget chain of its own, but a gadget in another plugin or theme, or WordPress core via the _wp_page_template meta key on hosts with a readable PEAR install and register_argc_argv enabled, could allow remote code execution.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check whether the Gravity Forms plugin is installed and its version (`3.1.2` or earlier is affected per the description)
- Check whether a Post Custom Field of input type List with a content template is enabled in any form

## Fix

- Gravity Forms: move to a version later than `3.1.2` (the fixed version is not stated in the sources)

## Timeline

- 2026-10-30T07:29:00+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-103039

## From the sources

The Gravity Forms plugin for WordPress is vulnerable to PHP Object Injection in all versions up to, and including, 3.1.2 via a Post Custom Field whose input type is List. This is due to GFFormsModel::create_post() passing the submitted value to WordPress' unrestricted global maybe_unserialize() rather than the plugin's own hardened GFCommon::maybe_unserialize(), which was added in 3.1.1 and passes allowed_classes => false precisely to prevent object instantiation. Where the field has a content template enabled, the submitted row reaches that call verbatim. This makes it possible for unauthenticated attackers to inject a PHP object into post meta. No PHP Object Injection gadget chain is present in the plugin itself; however, if a gadget chain is present via an additional plugin or theme, it could allow the attacker to perform actions such as remote code execution. Where the custom field is mapped to the protected _wp_page_template meta key, WordPress itself supplies the chain: validate_file() accepts non-scalars, WP_Theme::__toString() then resolves an attacker-controlled path, and on hosts with a readable PEAR install and register_argc_argv enabled this yields remote code execution.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_