# CVE-2026-12256: WordPress Fusion Builder plugin <= 3.15.3 - PHP Object Injection vulnerability

> An attacker can exploit PHP object injection in the Fusion Builder plugin to potentially execute arbitrary code on the WordPress site.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Jun 2026
- **Updated:** 1 Oct 2026
- **Also known as:** GHSA-5fx4-xh92-6xqm

## What is CVE-2026-12256?

CVE-2026-12256 is a high-severity unsafe deserialization vulnerability in ThemeFusion Fusion Builder, published on 16 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Deserialization of Untrusted Data vulnerability in ThemeFusion Fusion Builder fusion-builder allows Object Injection.This issue affects Fusion Builder: from n/a through 3.15.3.

Weakness: CWE-502 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2026-12256?


## How do I fix CVE-2026-12256?

No fix has been published for CVE-2026-12256 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-12256 being exploited?

There is no known exploitation of CVE-2026-12256 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-12256 and fix it if it is affected.

What it is: CVE-2026-12256 is a high-severity unsafe deserialization vulnerability in ThemeFusion Fusion Builder, published on 16 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-12256 in the wild and no public exploit code.

Affected product: ThemeFusion Fusion Builder. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-12256/ (Markdown: https://insights.sbomify.com/CVE-2026-12256/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-12256
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-12256
- OSV: https://osv.dev/vulnerability/CVE-2026-12256

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-12256/
Summaries are generated and may contain mistakes; the official description above is the record.