Nuxt dev server exposes generated appSecret through Vite file serving

Description

When no appSecret is configured (via NUXT_APP_SECRET, NITRO_APP_SECRET or runtimeConfig.appSecret), nuxt dev generates a development secret and stores it in <buildDir>/app-secret (by default .nuxt/app-secret). The build directory is inside the directories that Nuxt passes to Vite’s server.fs.allow, so the file can be fetched from the dev server:

Anyone who can read it can compute every secret derived from it with deriveSecret(), including the default password used by useSession, and so can forge session cookies accepted by that dev server.

Recommendation

Update the @nuxt/vite-builder package to the latest compatible version. Followings are version details:

• Affected version(s): >= 4.6.0, < 4.6.3
• Patched version(s): 4.6.3

References

• GHSA-3xf4-9g3c-4h4w
• CVE-2026-119201
• CWE-552
• CAPEC-310