---
title: "CVE-2026-8467: PhoenixStorybook: Unauthenticated remote code execution via HEEx template injection in phoenix_storybook playground"
url: https://erroneo.us/security/cve/CVE-2026-8467/
description: "CVE-2026-8467 (phoenix_storybook (Hex (Erlang/Elixir))): Code Injection vulnerability in phenixdigital phoenixstorybook allows unauthenticated remote code…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-05-20
date_modified: 2026-06-09
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-8467"
kev: false
cvss: 9.5
epss: 0.02059
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-8467: PhoenixStorybook: Unauthenticated remote code execution via HEEx template injection in phoenix_storybook playground

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 2.1% , percentile 81: FIRST’s model estimates a 2.1% chance of exploitation activity in the next 30 days, higher than 81% of all scored CVEs (elevated). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes phoenix_storybook (Hex (Erlang/Elixir)) >= 0.5.0, < 1.1.0, fixed in 1.1.0 . Check your lockfile, including transitive dependencies.

## What it is

Code Injection vulnerability in phenixdigital phoenixstorybook allows unauthenticated remote code execution via unsanitized attribute value interpolation in HEEx template generation. The psb-assign WebSocket event handler in 'Elixir.PhoenixStorybook.Story.PlaygroundPreviewLive':handleevent/3 accepts arbitrary attribute names and values from unauthenticated clients. These values are passed to 'Elixir.PhoenixStorybook.Helpers.ExtraAssignsHelpers':handlesetvariationassign/3, which stores them verbatim. When rendering, 'Elixir.PhoenixStorybook.Rendering.ComponentRenderer':attributesmarkup/1 interpolates binary attribute values directly into a HEEx template string as name=" " without escaping double quotes or HEEx expression delimiters. An attacker can supply a value containing a closing quote followed by a HEEx expression block (e.g. foo" injected={EXPR} bar="), which causes EXPR to be treated as an inline Elixir expression. The resulting template is compiled via EEx.compilestring/2 and executed via Code.evalquotedwithenv/3 with full Kernel imports and no sandbox, giving the attacker arbitrary code execution on the server. This issue affects phoenixstorybook from 0.5.0 before 1.1.0.

## Affected packages

- Hex (Erlang/Elixir) `phoenix_storybook` >= 0.5.0, < 1.1.0 → fixed: 1.1.0

## Affected products (CVE record)

- phenixdigital phoenix_storybook: 0.5.0 < 1.1.0
- phenixdigital phoenix_storybook: e35379dfe2ef1a71b141899e36f431017c55265d < 56ab8464d4375fa52db806148a06cce126ad481d

## Severity

- EEF CVSS 4.0: 9.5 `CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H`
- GitHub CVSS 4.0: 9.5 `CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 2.06% probability of exploitation activity in the next 30 days; percentile 81.

## Sources

- [github.com](https://github.com/phenixdigital/phoenix_storybook/security/advisories/GHSA-55hg-8qxv-qj4p)
- [github.com](https://github.com/phenixdigital/phoenix_storybook/commit/56ab8464d4375fa52db806148a06cce126ad481d)
- [GitHub Advisory GHSA-55hg-8qxv-qj4p](https://github.com/advisories/GHSA-55hg-8qxv-qj4p)
- [CVE.org record CVE-2026-8467](https://www.cve.org/CVERecord?id=CVE-2026-8467)
- [NVD entry CVE-2026-8467](https://nvd.nist.gov/vuln/detail/CVE-2026-8467)
- [cna.erlef.org](https://cna.erlef.org/cves/CVE-2026-8467.html)
- [osv.dev](https://osv.dev/vulnerability/EEF-CVE-2026-8467)

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Source page: https://erroneo.us/security/cve/CVE-2026-8467/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt