CVE-2026-44373 is a medium-severity (CVSS 5.3) vulnerability in nitro. O3 Security confirms whether CVE-2026-44373 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Nitro: Proxy scope bypass via percent-encoded path traversal in `routeRules`
Real-World Exposure
nitro📦nitropackReal-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
Nitro is a next generation server toolkit. Prior to 3.0.260429-beta, an attacker could bypass a proxy route rule by sending percent-encoded path traversal (..%2f) in the URL, causing Nitro to forward a request that the upstream resolved outside the configured scope. This vulnerability is fixed in 3.0.260429-beta.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | nitro | all versions | 3.0.260429-beta |
| 📦npm | nitropack | all versions | 2.13.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nitro. 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 nitro to 3.0.260429-beta or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44373 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-2026-44373 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-2026-44373. 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-2026-44373 in your dependencies?
O3 detects CVE-2026-44373 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.