Summary
The WebSocket functionality in Storybook's dev server, used to create and update stories, is vulnerable to WebSocket hijacking. This vulnerability only affects the Storybook dev server; production builds are not impacted.
Details
Exploitation requires a developer to visit a malicious website while their local Storybook dev server is running. Because the WebSocket connection does not validate the origin of incoming connections, a malicious site can silently send WebSocket messages to the local instance without any further user interaction.
If a Storybook dev server is intentionally exposed publicly (e.g. for design reviews or stakeholder demos) the risk is higher, as no malicious site visit is required. Any unauthenticated attacker can send WebSocket messages to it directly.
The vulnerability affects the WebSocket message handlers for creating and saving stories, which can be exploited via unauthorized WebSocket connections to achieve persistent XSS or Remote Code Execution (RCE).
Note: recent versions of Chrome have some protections against this, but Firefox does not.
Affected versions
8.1 and above. While the exploitable functionality was introduced in 8.1, the patch has been applied to 7.x as a precautionary measure given the underlying WebSocket behaviour.
Recommended actions
Update to one of the patched versions: 7.6.23, 8.6.17, 9.1.19, 10.2.10.
Impact
This vulnerability can lead to supply chain compromise. Key risks include:
- Remote Code Execution: The vulnerability can allow attackers to execute malicious code, with the extent of impact depending on the configuration. Server-side RCE is possible in non-default configurations, such as when stories are executed via portable stories in JSDOM, potentially allowing attackers to exfiltrate credentials and environment variables, access source code and the filesystem, establish backdoors, or pivot to internal network resources.
- Persistent XSS: Malicious payloads are written directly into story source files. If the malicious payload is committed to version control, it becomes part of the codebase and can propagate to deployed Storybook documentation sites, affecting developers and stakeholders who view them.
- Supply Chain Propagation: If the modified source files are committed, injected code can spread to other team members via git, execute in CI/CD pipelines, and affect shared component libraries used across multiple projects.
Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
storybook to 8.6.17 or later; storybook to 9.1.19 or later; storybook to 10.2.10 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2026-27148? CVE-2026-27148 is a high-severity cross-site scripting (XSS) vulnerability in storybook (npm), affecting versions >= 8.1.0, < 8.6.17. It is fixed in 8.6.17, 9.1.19, 10.2.10. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
- Which versions of storybook are affected by CVE-2026-27148? storybook (npm) versions >= 8.1.0, < 8.6.17 is affected.
- Is there a fix for CVE-2026-27148? Yes. CVE-2026-27148 is fixed in 8.6.17, 9.1.19, 10.2.10. Upgrade to this version or later.
- Is CVE-2026-27148 exploitable, and should I be worried? Whether CVE-2026-27148 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-27148 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-27148?
- Upgrade
storybookto 8.6.17 or later - Upgrade
storybookto 9.1.19 or later - Upgrade
storybookto 10.2.10 or later
- Upgrade