# CVE-2026-8809: Privilege escalation in Advanced Custom Fields: Extended

> Unauthenticated attackers can create administrator accounts by bypassing validation in Advanced Custom Fields: Extended if a public user creation form is configured.

- **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:** 28 May 2026
- **Updated:** 29 May 2026
- **Also known as:** GHSA-jvvq-c627-79xm

## What is CVE-2026-8809?

CVE-2026-8809 is a critical vulnerability in hwk-fr Advanced Custom Fields: Extended, published on 28 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The Advanced Custom Fields: Extended plugin for WordPress is vulnerable to Privilege Escalation via Validation Bypass in all versions up to and including 0.9.2.5. The vulnerability exists due to the after_validate_save_post() function unconditionally trusting the attacker-controlled _acf_post_id POST parameter — with no authentication or integrity verification — to select a cleanup branch that silently discards all validation errors not prefixed with acfe:. This makes it possible for unauthenticated attackers to suppress both the role allow-list validation error added by acfe_field_user_roles::validate_front_value() and the administrator-role capability guard error added by acfe_module_form_action_user::validate_action(), causing wp_insert_user() to execute with an attacker-supplied administrator role argument and resulting in the creation of a new administrator-level user account. Exploitation requires the target site to expose a public ACFE frontend form configured with a Create User action that maps a role field.

Weakness: CWE-269 (Improper Privilege Management)

## Which versions are affected by CVE-2026-8809?


## How do I fix CVE-2026-8809?

No fix has been published for CVE-2026-8809 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-8809 being exploited?

There is no known exploitation of CVE-2026-8809 in the wild and no public exploit code.

Public exploit code:

- Advanced Custom Fields: Extended <= 0.9.2.5 - Unauthenticated Privilege Escalation via Validation Bypass to '_acf_post_id' Parameter (github_poc): https://github.com/izxci/CVE-2026-8809

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-8809 and fix it if it is affected.

What it is: CVE-2026-8809 is a critical vulnerability in hwk-fr Advanced Custom Fields: Extended, published on 28 May 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-2026-8809 in the wild and no public exploit code.

Affected product: hwk-fr Advanced Custom Fields: Extended. 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-2026-8809/ (Markdown: https://insights.sbomify.com/CVE-2026-8809/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-8809
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-8809
- OSV: https://osv.dev/vulnerability/CVE-2026-8809

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-8809/
Summaries are generated and may contain mistakes; the official description above is the record.