CVE-2026-39363
CVE-2026-39363 is a Information Exposure vulnerability in vite. O3 Security confirms whether CVE-2026-39363 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Vite Affected by Arbitrary File Read via Vite Dev Server WebSocket
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, a proxy for how much of the ecosystem is exposed.
vitenpmDescription
Vite is a frontend tooling framework for JavaScript. From 6.0.0 to before 6.4.2, 7.3.2, and 8.0.5, if it is possible to connect to the Vite dev server’s WebSocket without an Origin header, an attacker can invoke fetchModule via the custom WebSocket event vite:invoke and combine file://... with ?raw (or ?inline) to retrieve the contents of arbitrary files on the server as a JavaScript string (e.g., export default "..."). The access control enforced in the HTTP request path (such as server.fs.allow) is not applied to this WebSocket-based execution path. This vulnerability is fixed in 6.4.2, 7.3.2, and 8.0.5.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | vite | ≥ 8.0.0&&< 8.0.5 | 8.0.5 |
| 📦npm | vite | ≥ 7.0.0&&< 7.3.2 | 7.3.2 |
| 📦npm | vite | ≥ 6.0.0&&< 6.4.2 | 6.4.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for vite. 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 vite to 8.0.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-39363 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-2026-39363 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-2026-39363. 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-2026-39363 in your dependencies?
O3 detects CVE-2026-39363 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.