# CVE-2026-82727: AshPhoenix Form.Auto leaks submitted params in an unknown _union_type error message

> Attackers can leak sensitive submitted parameters, such as passwords, into error logs and crash reports by triggering a union type mismatch in AshPhoenix Form.Auto.

- **Severity:** Low 2.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 31 Aug 2026
- **Updated:** 31 Aug 2026
- **Also known as:** EEF-CVE-2026-82727, GHSA-5xf4-hgcq-xw7v

## What is CVE-2026-82727?

CVE-2026-82727 is a low-severity vulnerability in ash-project ash_phoenix, published on 31 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Generation of Error Message Containing Sensitive Information vulnerability in ash-project ash_phoenix writes the entire raw submitted param map into an exception message, so secrets submitted alongside a union form field leak into logs, crash reports and the dev error page.

When AshPhoenix.Form.Auto builds a union sub-form and the submitted _union_type does not match a configured type, both raise sites built the message with inspect(params, pretty: true), embedding the full untrusted param map, and also inspected the internal union constraints[:types]. Because the message is constructed by the library rather than Phoenix's parameter logger, config :phoenix, :filter_parameters never redacts it. An attacker controls both the trigger and the contents: submitting %{"_union_type" => "nope", "password" => "..."} puts the password verbatim in the raised message. The fix reports only the offending _union_type and the valid type names, dropping the param and constraints dumps.

This issue affects ash_phoenix: from 1.2.17 before 2.3.25.

Weakness: CWE-209 (Generation of Error Message Containing Sensitive Information)

## Which versions are affected by CVE-2026-82727?

1 open source package ship an affected version, including ash_phoenix.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `ash_phoenix` | Hex | From 1.2.17 | 2.3.25 |

## How do I fix CVE-2026-82727?

Upgrade ash_phoenix to 2.3.25 or later.

## Is CVE-2026-82727 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-82727 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-82727 and fix it if it is affected.

What it is: CVE-2026-82727 is a low-severity vulnerability in ash-project ash_phoenix, published on 31 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-82727 exists.

Affected packages and fixed versions:
- ash_phoenix (Hex): affected from 1.2.17; fixed in 2.3.25

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-2026-82727/ (Markdown: https://insights.sbomify.com/CVE-2026-82727/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-82727
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-82727
- OSV: https://osv.dev/vulnerability/CVE-2026-82727

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-82727/
Summaries are generated and may contain mistakes; the official description above is the record.