CVE-2026-71321

Nuxt: Unauthenticated CPU exhaustion parsing and hashing the Nuxt island endpoint body before hash validation

Workarounds

Put a small request-body limit in front of /__nuxt_island/ at your reverse proxy / edge (islands legitimately send only a compact props payload), or disable server components if unused.

The internal island renderer endpoint (/__nuxt_island/...) decodes and hashes attacker-controlled request input before it validates the URL-resident hash. An unauthenticated POST /__nuxt_island/<name>_<anything>.json with a large JSON body (for example ~4.6 MB / 150k keys) is fully read, destr-parsed, and run through ohash before the request is rejected with a 400. Because Nitro runs on a single event loop, this both wastes CPU on the doomed request and delays every concurrent request. A low request rate is enough to degrade or stall the server. No valid hash and no authentication are required.

The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.

CVE-2026-71321 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. 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 (4.5.1, 3.21.10); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

Fixed in [email protected] and [email protected]. The island handler now enforces a raw body-size cap (413) and a JSON nesting-depth cap (400) before parsing or hashing, so oversized or deeply nested input is rejected cheaply.

1. What is CVE-2026-71321? CVE-2026-71321 is a high-severity allocation of resources without limits or throttling vulnerability in nuxt (npm), affecting versions >= 4.0.0, < 4.5.1. It is fixed in 4.5.1, 3.21.10. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
2. How severe is CVE-2026-71321? CVE-2026-71321 has a CVSS score of 7.5 (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 nuxt are affected by CVE-2026-71321? nuxt (npm) versions >= 4.0.0, < 4.5.1 is affected.
4. Is there a fix for CVE-2026-71321? Yes. CVE-2026-71321 is fixed in 4.5.1, 3.21.10. Upgrade to this version or later.
5. Is CVE-2026-71321 exploitable, and should I be worried? Whether CVE-2026-71321 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-2026-71321 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-2026-71321?
   • Upgrade nuxt to 4.5.1 or later
   • Upgrade nuxt to 3.21.10 or later

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