CVE-2026-33331

A Stored Cross-Site Scripting (XSS) vulnerability exists in the OpenAPI documentation generation of orpc. If an attacker can control any field within the OpenAPI specification (such as info.description), they can break out of the JSON context and execute arbitrary JavaScript when a user views the generated API documentation.
In the packages/openapi/src/plugins/openapi-reference.ts file, the renderDocsHtml() function takes an OpenAPI spec object and embeds it directly into the HTML response using a template literal:

<script id="spec" type="application/json">${JSON.stringify(spec)}</script>

The JSON.stringify() function does not escape HTML characters like < or >. Therefore, if an attacker provides a string containing

If an application generates its OpenAPI specifications dynamically based on user-controlled inputs (or if a rogue developer modifies the spec), it leads to Stored XSS. When an administrator or developer views the API docs, the script executes in their browser, potentially leading to session hijacking or unauthorized API calls on their behalf.

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.

CVE-2026-33331 has a CVSS score of 8.2 (High). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.13.9); upgrading removes the vulnerable code path.

Kodem intelligence

Do not use raw JSON.stringify() to embed data directly into HTML templates. Instead, safely serialize the JSON by escaping HTML-sensitive characters (like <** and **>) or use a secure HTML serialization library (such as serialize-javascript or devalue) before embedding it into the

1. What is CVE-2026-33331? CVE-2026-33331 is a high-severity cross-site scripting (XSS) vulnerability in @orpc/openapi (npm), affecting versions <= 1.13.8. It is fixed in 1.13.9. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. How severe is CVE-2026-33331? CVE-2026-33331 has a CVSS score of 8.2 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of @orpc/openapi are affected by CVE-2026-33331? @orpc/openapi (npm) versions <= 1.13.8 is affected.
4. Is there a fix for CVE-2026-33331? Yes. CVE-2026-33331 is fixed in 1.13.9. Upgrade to this version or later.
5. Is CVE-2026-33331 exploitable, and should I be worried? Whether CVE-2026-33331 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
6. What actually determines whether CVE-2026-33331 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.
7. How do I fix CVE-2026-33331? Upgrade @orpc/openapi to 1.13.9 or later.