CVE-2026-59149 is a medium-severity (CVSS 6.5) Path Traversal vulnerability in @mockoon/commons-server. O3 Security confirms whether CVE-2026-59149 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Mockoon: Path traversal in templated `filePath` lets a request escape the served directory (prefix-only base check)
Real-World Exposure
@mockoon/commons-server📦@mockoon/cliReal-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
Mockoon provides way to design and run mock APIs. Prior to 9.7.0, a FILE response whose filePath embeds request data is confined by getSafeFilePath in packages/commons-server/src/libs/server/server.ts with resolvedPath.startsWith(staticBaseDir). That prefix test has no path-separator boundary, so a ../-escaped path whose absolute form string-prefixes the base directory passes, allowing an unauthenticated client to read files from sibling paths outside the served directory through HTTP sendFile, WebSocket, or callbacks. This issue is fixed in version 9.7.0.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @mockoon/commons-server | all versions | 9.7.0 |
| 📦npm | @mockoon/cli | all versions | 9.7.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @mockoon/commons-server. 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 @mockoon/commons-server to 9.7.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-59149 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-2026-59149 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-2026-59149. 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-2026-59149 in your dependencies?
O3 detects CVE-2026-59149 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.