CVE-2026-25766 is a medium-severity (CVSS 5.3) Path Traversal vulnerability in github.com/labstack/echo/v5. O3 Security confirms whether CVE-2026-25766 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Echo has a Windows path traversal via backslash in middleware.Static default filesystem
Real-World Exposure
github.com/labstack/echo/v5Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Echo is a Go web framework. In versions 5.0.0 through 5.0.2 on Windows, Echo’s middleware.Static using the default filesystem allows path traversal via backslashes, enabling unauthenticated remote file read outside the static root. In middleware/static.go, the requested path is unescaped and normalized with path.Clean (URL semantics). path.Clean does not treat \ as a path separator, so ..\ sequences remain in the cleaned path. The resulting path is then passed to currentFS.Open(...). When the filesystem is left at the default (nil), Echo uses defaultFS which calls os.Open (echo.go:792). On Windows, os.Open treats \ as a path separator and resolves ..\, allowing traversal outside the static root. Version 5.0.3 fixes the issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/labstack/echo/v5 | ≥ 5.0.0&&< 5.0.3 | 5.0.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/labstack/echo/v5. 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 github.com/labstack/echo/v5 to 5.0.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-25766 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-2026-25766 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-2026-25766. 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-2026-25766 in your dependencies?
O3 detects CVE-2026-25766 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.