CVE-2026-45670
Fix: nuxt/nuxt#35051CVE-2026-45670 is a CWE-749 vulnerability in @nuxt/rspack-builder. O3 Security confirms whether CVE-2026-45670 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Nuxt: Dev server exposes built source over LAN to malicious sites (incomplete fix for GHSA-4gf7-ff8x-hq99)
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-45670.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@nuxt/rspack-buildernpm@nuxt/webpack-buildernpmDescription
Nuxt is an open-source web development framework for Vue.js. In @nuxt/rspack-builder and @nuxt/webpack-builder versions 3.15.4 to before 3.21.6, and 4.0.0-alpha.1 to before 4.4.6, there is an incomplete fix for GHSA-4gf7-ff8x-hq99. Source code may be stolen during dev when using the webpack / rspack builder if the dev server is bound to a non-loopback address (e.g. nuxt dev --host) and the developer opens a malicious site on the same network. This issue has been patched in versions 3.21.6 and 4.4.6.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @nuxt/rspack-builder | ≥ 3.15.4&&< 3.21.6 | 3.21.6 |
| 📦npm | @nuxt/rspack-builder | ≥ 4.0.0-alpha.1&&< 4.4.6 | 4.4.6 |
| 📦npm | @nuxt/webpack-builder | ≥ 3.15.4&&< 3.21.6 | 3.21.6 |
| 📦npm | @nuxt/webpack-builder | ≥ 4.0.0-alpha.1&&< 4.4.6 | 4.4.6 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @nuxt/rspack-builder. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update @nuxt/rspack-builder to 3.21.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-45670 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-45670 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-45670. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-45670 in your dependencies?
O3 detects CVE-2026-45670 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.