# CVE-2026-3891: Pix for WooCommerce <= 1.5.0 - Unauthenticated Arbitrary File Upload

> Unauthenticated attackers can upload arbitrary files via missing validation, potentially leading to remote code execution on the server.

- **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:** 13 Mar 2026
- **Updated:** 8 Apr 2026
- **Also known as:** GHSA-fpj4-w3j6-3v3w

## What is CVE-2026-3891?

CVE-2026-3891 is a critical vulnerability in linknacional Pix for WooCommerce, published on 13 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The Pix for WooCommerce plugin for WordPress is vulnerable to arbitrary file uploads due to missing capability check and missing file type validation in the 'lkn_pix_for_woocommerce_c6_save_settings' function in all versions up to, and including, 1.5.0. This makes it possible for unauthenticated attackers to upload arbitrary files on the affected site's server which may make remote code execution possible.

Weakness: CWE-434 (Unrestricted Upload of File with Dangerous Type)

## Which versions are affected by CVE-2026-3891?


## How do I fix CVE-2026-3891?

No fix has been published for CVE-2026-3891 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-3891 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-3891 exists.

Public exploit code:

- PoC for CVE-2026-3891 — Unauthenticated Arbitrary File Upload leading to Remote Code Execution in Pix for WooCommerce <= 1.5.0 (github_poc): https://github.com/m4sh-wacker/CVE-2026-3891-Pix-for-WooCommerce-Plugin-Exploit
- Pix for WooCommerce <= 1.5.0 - Unauthenticated Arbitrary File Upload (CVE-2026-3891) PoC (github_poc): https://github.com/joshuavanderpoll/CVE-2026-3891
- Pix for WooCommerce <= 1.5.0 - Unauthenticated Arbitrary File Upload (github_poc): https://github.com/Nxploited/CVE-2026-3891
- Pix for WooCommerce Unauthenticated File Upload via certificate_crt_path Parameter | CVSS 9.8 (github_poc): https://github.com/shinthink/CVE-2026-3891
- CVE-2026-3891 Mass Scanning (github_poc): https://github.com/AnggaTechI/Mass-Scanner-CVE-2026-3891
- PoC for CVE-2026-3891 – Unauthenticated File Upload RCE in Pix for WooCommerce ≤ 1.5.0. Automated nonce retrieval, PHP upload, and command execution. (github_poc): https://github.com/Ch4120N/CVE-2026-3891

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-3891 and fix it if it is affected.

What it is: CVE-2026-3891 is a critical vulnerability in linknacional Pix for WooCommerce, published on 13 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-3891 exists.

Affected product: linknacional Pix for WooCommerce. 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-2026-3891/ (Markdown: https://insights.sbomify.com/CVE-2026-3891/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-3891
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-3891
- OSV: https://osv.dev/vulnerability/CVE-2026-3891

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-3891/
Summaries are generated and may contain mistakes; the official description above is the record.