GHSA-72c6-fx6q-fr5w
CRITICALGHSA-72c6-fx6q-fr5w is a critical-severity (CVSS 9.1) vulnerability in @fastify/middie. O3 Security confirms whether GHSA-72c6-fx6q-fr5w is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
@fastify/middie vulnerable to middleware authentication bypass in child plugin scopes
Real-World Exposure
@fastify/middieReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.
Description
Impact
@fastify/middie v9.3.1 and earlier incorrectly re-prefixes middleware paths when propagating them to child plugin scopes. When a child plugin is registered with a prefix that overlaps with a parent-scoped middleware path, the middleware path is modified during inheritance and silently fails to match incoming requests.
This results in complete bypass of middleware security controls for all routes defined within affected child plugin scopes, including nested (grandchild) scopes. Authentication, authorization, rate limiting, and any other middleware-based security mechanisms are skipped. No special request crafting or configuration is required.
This is the same vulnerability class as GHSA-hrwm-hgmj-7p9c (CVE-2026-33807) in @fastify/express.
Patches
Upgrade to @fastify/middie v9.3.2 or later.
Workarounds
None. Upgrade to the patched version.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @fastify/middie | all versions | 9.3.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @fastify/middie. 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 @fastify/middie to 9.3.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-72c6-fx6q-fr5w 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 GHSA-72c6-fx6q-fr5w 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 GHSA-72c6-fx6q-fr5w. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-72c6-fx6q-fr5w in your dependencies?
O3 detects GHSA-72c6-fx6q-fr5w across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.