CVE-2025-53109
CVE-2025-53109 is a CWE-59 vulnerability in @modelcontextprotocol/server-filesystem. O3 Security confirms whether CVE-2025-53109 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Model Context Protocol Servers Vulnerable to Path Validation Bypass via Prefix Matching and Symlink Handling
Blast Radius
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
@modelcontextprotocol/server-filesystemnpmDescription
Model Context Protocol Servers is a collection of reference implementations for the model context protocol (MCP). Versions of Filesystem prior to 0.6.4 or 2025.7.01 could allow access to unintended files via symlinks within allowed directories. Users are advised to upgrade to 0.6.4 or 2025.7.01 resolve.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @modelcontextprotocol/server-filesystem | all versions | No fix |
| 📦npm | @modelcontextprotocol/server-filesystem | ≥ 2025.1.14&&< 2025.7.1 | 2025.7.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @modelcontextprotocol/server-filesystem. 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
No patched version of @modelcontextprotocol/server-filesystem has shipped for CVE-2025-53109 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
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-2025-53109 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-2025-53109. 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-2025-53109 in your dependencies?
O3 detects CVE-2025-53109 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.