CVE-2026-119199 in Nuxt
Summary
by MITRE • 10/29/2026
Nuxt is an open-source web development framework for Vue.js. From 3.0.0 until 4.6.3, the Nuxt development server can expose the Nitro 2 development bundle at <buildDir>/dev/index.mjs through Vite file serving when the server is reachable over HTTP. Nitro inlines private runtimeConfig values resolved at build time into that bundle, including secrets configured in nuxt.config, and Nuxt 4.6.0 and later also inline the generated development appSecret. The default localhost binding limits remote exposure, production builds and Nitro 3 are not affected, and runtime configuration supplied only through NUXT_* environment variables at server startup is not inlined. This issue is fixed in version 4.6.3.
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Analysis
by VulDB Data Team • 10/29/2026
The vulnerability identified involves the Nuxt web development framework, specifically affecting versions from 3.0.0 up to 4.6.3. The core technical flaw resides within the Nitro server engine's handling of runtime configuration during the build process for the development environment. When a developer runs the local development server, which is bound by default to localhost and thus typically inaccessible remotely, Nuxt utilizes Vite to serve static assets including source maps and bundle files. In this specific context, the framework exposes an endpoint at /dev/index.mjs that contains the Nitro 2 development bundle. This bundle is not merely a standard JavaScript file but includes inlined private runtime configuration values that were resolved during the build phase. These values encompass sensitive secrets defined within the nuxt.config.js file as well as, starting from version 4.6.0, the generated application secret used for session management and cryptographic operations.
The operational impact of this vulnerability is significant if an attacker can gain access to the development server interface. Although the default configuration binds the server to localhost, limiting exposure primarily to local network attacks or scenarios where port forwarding is misconfigured, any remote reachability over HTTP allows for direct exploitation. An adversary who accesses the /dev/index.mjs endpoint can extract these inlined secrets and application keys. The compromise of runtime config values may lead to unauthorized access to backend services if those configurations include database credentials or API keys. Furthermore, the exposure of the appSecret undermines the integrity of session tokens and signed cookies, potentially allowing attackers to forge authentication tokens, escalate privileges, or perform account takeover attacks against users interacting with the application during development or testing phases where such misconfigurations might persist longer than in production environments.
This vulnerability aligns with CWE-798: Use of Hard-coded Credentials, as sensitive information is embedded directly into the client-side accessible bundle rather than being kept strictly server-side or injected securely at runtime via environment variables that are not bundled. From a tactical perspective within the MITRE ATT&CK framework, this behavior facilitates Credential Access and potentially Initial Access if combined with other vectors like SSRF or misconfigured network policies. It is important to note that production builds are unaffected because they do not expose development-specific bundles containing inlined secrets. Similarly, Nitro version 3 and later versions have addressed this issue by changing how configuration values are handled, ensuring they are not inlined into the client-facing bundle. Additionally, configurations supplied exclusively through NUXT_* environment variables at server startup remain secure as these are processed dynamically without being baked into the static development assets.
Mitigation strategies primarily involve upgrading to version 4.6.3 or later where this flaw has been patched. For environments that cannot immediately upgrade, developers should ensure that the Nuxt development server is strictly bound to localhost and not exposed through reverse proxies or port forwarding rules unless absolutely necessary for remote debugging scenarios requiring secure tunneling with authentication enabled. It is also critical to audit nuxt.config.js files to avoid placing high-value secrets in configuration objects intended for build-time resolution, preferring instead to inject them via environment variables at runtime which are excluded from the bundled output by design. Regular security audits of development toolchains and strict adherence to least-privilege principles regarding network exposure during active development cycles will further reduce the risk surface associated with such framework-level vulnerabilities.