# CVE-2026-8469: Unauthenticated denial-of-service via BEAM atom table exhaustion in phoenix_storybook

> Unauthenticated attackers can crash the BEAM node by exhausting the atom table via unvalidated string-to-atom conversions in phoenix_storybook.

- **Severity:** High 8.2 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 20 May 2026
- **Updated:** 27 May 2026
- **Also known as:** EEF-CVE-2026-8469, GHSA-833p-95jq-929q

## What is CVE-2026-8469?

CVE-2026-8469 is a high-severity denial of service vulnerability in phenixdigital phoenix_storybook, published on 20 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Allocation of Resources Without Limits or Throttling vulnerability in phenixdigital phoenix_storybook allows unauthenticated denial-of-service via BEAM atom table exhaustion.

Multiple LiveView event handlers convert user-supplied event parameter strings to atoms using String.to_atom/1 without validation: 'Elixir.PhoenixStorybook.ExtraAssignsHelpers':handle_set_variation_assign/3 interns every key of the psb-assign params map; 'Elixir.PhoenixStorybook.ExtraAssignsHelpers':handle_toggle_variation_assign/3 interns the "attr" value from psb-toggle events; 'Elixir.PhoenixStorybook.ExtraAssignsHelpers':to_variation_id/2 interns elements of "variation_id"; and 'Elixir.PhoenixStorybook.ExtraAssignsHelpers':to_value/4 interns raw string values for attributes declared as :atom or :boolean. BEAM atoms are never garbage-collected, so each unique attacker-controlled string is a permanent allocation. Once the atom table ceiling (~1,048,576 atoms) is reached, the entire BEAM node aborts, taking down all applications running on it.

This issue affects phoenix_storybook from 0.2.0 before 1.1.0.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2026-8469?

3 open source packages ship an affected version, including phoenix_storybook.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `phoenix_storybook` | Hex | From 0.2.0 | 1.1.0 |
| `phoenix_storybook` | Hex | From 0.2.0 | 1.1.0 |
| `phoenix_storybook` | Hex | From 0.2.0 | 1.1.0 |

## How do I fix CVE-2026-8469?

Upgrade phoenix_storybook to 1.1.0 or later.

## Is CVE-2026-8469 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-8469 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-8469 and fix it if it is affected.

What it is: CVE-2026-8469 is a high-severity denial of service vulnerability in phenixdigital phoenix_storybook, published on 20 May 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-2026-8469 exists.

Affected packages and fixed versions:
- phoenix_storybook (Hex): affected from 0.2.0; fixed in 1.1.0
- phoenix_storybook (Hex): affected from 0.2.0; fixed in 1.1.0
- phoenix_storybook (Hex): affected from 0.2.0; fixed in 1.1.0

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-2026-8469/ (Markdown: https://insights.sbomify.com/CVE-2026-8469/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-8469
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-8469
- OSV: https://osv.dev/vulnerability/CVE-2026-8469

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-8469/
Summaries are generated and may contain mistakes; the official description above is the record.