# Storybook Dev Server is Vulnerable to WebSocket Hijacking

Advisory record · `GHSA-mjf5-7g4m-gx5w`

- **Identifiers:** `GHSA-mjf5-7g4m-gx5w` · `CVE-2026-27148`
- **State:** Confirmed
- **Severity:** CVSS 8.9 High
- **Critical:** No
- **Weakness (CWE):** [CWE-74](https://cwe.mitre.org/data/definitions/74.html) · [CWE-79](https://cwe.mitre.org/data/definitions/79.html) · [CWE-346](https://cwe.mitre.org/data/definitions/346.html) · [CWE-1385](https://cwe.mitre.org/data/definitions/1385.html)
- **Tags:** [Other injection](https://agentprime.io/advisories/tag/injection.md) · [Cross-site scripting (XSS)](https://agentprime.io/advisories/tag/xss.md) · [CWE-346](https://agentprime.io/advisories/tag/cwe-346.md) · [CWE-1385](https://agentprime.io/advisories/tag/cwe-1385.md)
- **Published:** 26 Feb 2026
- **Updated:** 26 Feb 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 26 Feb 2026, 15:16 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `storybook` (npm): affected `>=8.1.0, <8.6.17 || >=8.7.0-alpha.0, <9.1.19 || >=10.0.0-beta.0, <10.2.10`; fixed in `8.6.17`, `9.1.19`, `10.2.10`

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 8.9 High, CVSS 4.0: `CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0063, the 50th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

This record came from the full history of the GitHub Advisory Database, published 26 Feb 2026. New records show when each source confirmed them.

## Sources

- [GitHub Advisory Database: GHSA-mjf5-7g4m-gx5w](https://github.com/advisories/GHSA-mjf5-7g4m-gx5w)
- [OSV: GHSA-mjf5-7g4m-gx5w](https://osv.dev/vulnerability/GHSA-mjf5-7g4m-gx5w)
- <https://github.com/storybookjs/storybook/security/advisories/GHSA-mjf5-7g4m-gx5w>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-27148>
- <https://github.com/storybookjs/storybook/commit/0affdf928bd6fafbadfb1dfe22ce6104805e10e8>
- <https://github.com/storybookjs/storybook/commit/54689a8add18ea75d628c540f4bc677592a1e685>
- <https://github.com/storybookjs/storybook/commit/b8cfa77c73940c140acdcd8a06ab1ea913c44761>
- <https://github.com/storybookjs/storybook/commit/d34085f39c647f5c23c3a3b2d197c18602fcf876>
- <https://github.com/storybookjs/storybook>
- <https://github.com/storybookjs/storybook/releases/tag/v10.2.10>
- <https://github.com/storybookjs/storybook/releases/tag/v7.6.23>
- <https://github.com/storybookjs/storybook/releases/tag/v8.6.17>
- <https://github.com/storybookjs/storybook/releases/tag/v9.1.19>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-mjf5-7g4m-gx5w>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-mjf5-7g4m-gx5w/>. Everything for agents: <https://agentprime.io/llms.txt>.