# CVE-2026-52889: Formie: Server-Side Template Injection in Formie Hidden field defaults

> Unauthenticated attackers can achieve remote code execution or data disclosure by injecting Twig syntax into Hidden field defaults in Formie.

- **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:** Yes
- **Published:** 19 Aug 2026
- **Updated:** 19 Aug 2026
- **Also known as:** GHSA-565m-g33j-jq96

## What is CVE-2026-52889?

CVE-2026-52889 is a critical code injection vulnerability in verbb formie, published on 19 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Formie is a Craft CMS plugin for creating forms. Prior to 3.1.27, Formie can pass request-derived Hidden field defaults such as HTTP User Agent, Referer URL, Current URL, Current URL without Query String, Query Parameter, and Cookie Value to Craft's Twig rendering layer during front-end form rendering. An unauthenticated attacker can place Twig syntax in one of these request-controlled inputs when a public form contains an affected Hidden field. Hidden::getFrontEndInputOptions() then assigns the value to defaultValue and calls renderString, causing server-side template evaluation rather than treating the request data as a plain string. Depending on the Craft site configuration and available Twig capabilities, exploitation can disclose sensitive information, modify application state, or achieve remote code execution. This issue is fixed in version 3.1.27.

Weakness: CWE-1336 (Improper Neutralization of Special Elements Used in a Template Engine)

## Which versions are affected by CVE-2026-52889?

2 open source packages ship an affected version, including verbb/formie.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `verbb/formie` | Packagist | All versions | 3.1.27 |
| `verbb/formie` | Packagist | All versions | 3.1.27 |

## How do I fix CVE-2026-52889?

Upgrade verbb/formie to 3.1.27 or later.

## Is CVE-2026-52889 being exploited?

There is no known exploitation of CVE-2026-52889 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-52889 and fix it if it is affected.

What it is: CVE-2026-52889 is a critical code injection vulnerability in verbb formie, published on 19 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-2026-52889 in the wild and no public exploit code.

Affected packages and fixed versions:
- verbb/formie (Packagist): affected all versions; fixed in 3.1.27
- verbb/formie (Packagist): affected all versions; fixed in 3.1.27

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-2026-52889/ (Markdown: https://insights.sbomify.com/CVE-2026-52889/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-52889
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-52889
- OSV: https://osv.dev/vulnerability/CVE-2026-52889

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-52889/
Summaries are generated and may contain mistakes; the official description above is the record.