Storybook dev server flaw lets websites change your files: upgrade

What it is: The Storybook preview does not properly check where connection requests come from. While a Storybook dev server is running, a malicious website may be able to make unauthorized changes to files in your project. Under additional conditions, a changed file could be run by a local tool with your own privileges. The advisory is tracked as GHSA-f2ph-cmg5-wxc8 and CVE-2026-114125, rated critical (CVSS 4.0 score 9.4).

Who is affected: Anyone who runs a Storybook dev server on an affected version of the storybook npm package. Related packages are also listed: @storybook/core, @storybook/core-server, @storybook/experimental-addon-test, @storybook/addon-vitest and @storybook/addon-mcp.

You are not affected if you run a dev server that you never open in a web browser (for example headless automation or MCP clients), or if you only run or visit a built version of Storybook.

Is it being exploited? The advisory says the Storybook team is not aware of exploitation in the wild.

What to do: - Upgrade to a patched version before running the dev server again: 8.6.19, 9.1.21, 10.6.2 or 11.0.0-alpha.6, depending on your major version. - If you cannot upgrade right away, do not run an affected dev server until you can. - Recent Chrome and Firefox may ask permission before a website connects to a local service. This lowers the risk but does not remove it. Do not grant it to sites you do not trust. - Storybook has changed some network-related defaults, including in versions 8 and 9. If your team relies on those features, check the vendor's advisory for the feature flags that control them.