CVE-2026-8467Public exploitNetwork attack vector

Unauthenticated code execution via HEEx attribute injection

Published May 20, 2026 · Updated May 20, 2026

Code injection in PhoenixStorybook 0.5.0 through 1.0.0 allows remote attackers to execute arbitrary server code via WebSocket input. ComponentRenderer.attributes_markup/1 inserts unescaped binary attribute values into a HEEx string that EEx.compile_string/2 compiles and Code.eval_quoted_with_env/3 evaluates without a sandbox. Any unauthenticated client that can reach a story with the Playground tab can run operating-system commands with the server process's privileges.

CVSS severity9.5
Critical
EPSS probability2.11%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Code injection in PhoenixStorybook 0.5.0 through 1.0.0 allows remote attackers to execute arbitrary server code via WebSocket input. ComponentRenderer.attributes_markup/1 inserts unescaped binary attribute values into a HEEx string that EEx.compile_string/2 compiles and Code.eval_quoted_with_env/3 evaluates without a sandbox. Any unauthenticated client that can reach a story with the Playground tab can run operating-system commands with the server process's privileges.

The record

CVE
CVE-2026-8467
Published
May 20, 2026
Updated
May 20, 2026
Vendor
Phenix Technologies
Product
PhoenixStorybook
Classifications
CWE-94, T1059
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 20, 2026CVE publishedPublication date reported by the CVE source.
  2. May 20, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0.5.0 <1.1.0
  2. Affected versionversion=e35379dfe2ef1a71b141899e36f431017c55265d <56ab8464d4375fa52db806148a06cce126ad481d

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Phenix Technologies · PhoenixStorybookversion=0.5.0 <1.1.0; version=e35379dfe2ef1a71b141899e36f431017c55265d <56ab8464d4375fa52db806148a06cce126ad481d

Published CVSS scores

9.5Erlang Ecosystem Foundation CNACVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-94Improper Control of Generation of Code ('Code Injection')
T1059Command and Scripting Interpreter

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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