# CVE-2026-18431: Avada <= 7.16 and Fusion Builder <= 3.16 - Unauthenticated Remote Code Execution via Arbitrary File Write

> Unauthenticated attackers can write arbitrary files to the server, leading to remote code execution and full site compromise in Avada and Fusion Builder.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 26 Aug 2026
- **Updated:** 27 Aug 2026
- **Also known as:** GHSA-hm9x-g2wh-6xw7

## What is CVE-2026-18431?

CVE-2026-18431 is a critical vulnerability in ThemeFusion Avada (Fusion) Builder, published on 26 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The Avada theme for WordPress is vulnerable to Arbitrary File Write in all versions up to, and including, 7.16 when the Fusion Builder plugin is installed and active in versions up to, and including, 3.16. This is due to a chain of authorization and input validation weaknesses across the two components that makes it possible for unauthenticated attackers to write attacker-controlled files to the server. This can be used to create and execute arbitrary PHP files, resulting in remote code execution and complete site compromise. Successful exploitation requires both Avada and Fusion Builder to be installed and active, as well as certain administrator-authored content to be present.

Weakness: CWE-862 (Missing Authorization)

## Which versions are affected by CVE-2026-18431?


## How do I fix CVE-2026-18431?

No fix has been published for CVE-2026-18431 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-18431 being exploited?

There is no known exploitation of CVE-2026-18431 in the wild and no public exploit code.

Public exploit code:

- CVE-2026-18431 - Draft or TODO (github_poc): https://github.com/HORKimhab/CVE-2026-18431

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-18431 and fix it if it is affected.

What it is: CVE-2026-18431 is a critical vulnerability in ThemeFusion Avada (Fusion) Builder, published on 26 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-18431 in the wild and no public exploit code.

Affected product: ThemeFusion Avada (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-2026-18431/ (Markdown: https://insights.sbomify.com/CVE-2026-18431/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-18431
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-18431
- OSV: https://osv.dev/vulnerability/CVE-2026-18431

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-18431/
Summaries are generated and may contain mistakes; the official description above is the record.