---
id: "CVE-2026-118655"
kind: "vulnerability"
aliases: ["CVE-2026-118655", "GHSA-xwq5-6cqp-vx96"]
title: "Echo has a Static Middleware Double-Unescape Path Traversal"
severity: "medium"
cvss: 5.9
epss: null
exploited: false
status: "open"
category: "package"
products: [{"name": "github.com/labstack/echo/v5", "fixed": ["5.2.0"], "affected": "< 5.2.0", "ecosystem": "go"}, {"name": "github.com/labstack/echo/v4", "fixed": ["4.15.3"], "affected": "< 4.15.3", "ecosystem": "go"}]
ecosystems: ["go"]
tags: ["cwe-174", "echo", "go", "package", "self-hosted"]
not_affected_if: ["no-static-middleware", "static-middleware-scoped-to-route"]
published_at: "2026-10-28T20:17:22+00:00"
first_seen_at: "2026-10-28T20:35:10+00:00"
updated_at: "2026-10-28T21:07:44+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-118655", "first_seen_at": "2026-10-28T20:35:10+00:00"}, {"source": "ghsa", "url": "https://github.com/advisories/GHSA-xwq5-6cqp-vx96", "first_seen_at": "2026-10-28T21:07:44+00:00"}]
---

# Echo has a Static Middleware Double-Unescape Path Traversal

Echo's middleware.Static decodes the request path a second time, so double-encoded path separators can be rebuilt before the filesystem lookup. An attacker can reach files under a route that is supposed to be guarded when the static middleware is registered globally.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- go:github.com/labstack/echo/v5 affected < 5.2.0 fixed 5.2.0
- go:github.com/labstack/echo/v4 affected < 4.15.3 fixed 4.15.3

## How to check

- Check the Echo version in go.mod with `grep labstack/echo go.mod`; versions before `4.15.3` and `5.2.0` are affected.
- Look for `middleware.Static` registered with `e.Use(...)` at the top level, which applies it to all routes.

## Fix

- Upgrade the Go module `github.com/labstack/echo/v4` to `4.15.3` or later.
- Upgrade `github.com/labstack/echo/v5` to `5.2.0` or later.

## Timeline

- 2026-10-28T20:35:10+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-118655
- 2026-10-28T21:07:44+00:00 ghsa https://github.com/advisories/GHSA-xwq5-6cqp-vx96

## From the sources

## Summary

Commit a9ede66a (PR #3006, issue #2599) silently fixed a path traversal vulnerability in the Echo web framework's static file middleware.

## Vulnerability

The static middleware double-unescaped URL paths. Go's net/http already decodes Request.URL.Path, but middleware/static.go unconditionally called url.PathUnescape() again:

```go
// BEFORE (vulnerable)
pathUnescape := true
```

This reassembled path traversal sequences from double-encoded input. An attacker could send GET /%2e%2e%2fsecret.txt or /..%252fsecret.txt and the double-unescape would produce ../secret.txt.

## Fix
```go
// AFTER (fixed)
pathUnescape := false
```

The commit's test TestStatic_percentEncodedTraversalIsBlocked explicitly verifies traversal vectors are blocked.

## Impact
Arbitrary file read from server filesystem via percent-encoded path traversal.

## References
- Fix: https://github.com/labstack/echo/commit/a9ede66a
- Issue: https://github.com/labstack/echo/issues/2599
- PR: https://github.com/labstack/echo/pull/3006

## Patches

Fixed in `github.com/labstack/echo/v5` v5.2.0 and `github.com/labstack/echo/v4` v4.15.3, where the Static middleware stopped unescaping an already decoded path. Maintainer analysis: reading files outside the configured root could not be reproduced; the confirmed impact was that a double-encoded slash (`%252F`) could reach a file under a guarded route when the Static middleware is registered globally. Upgrade to v5.4.0 / v4.16.0 or later, which also includes related fixes for encoded and dot-segment paths.

## Workarounds

Keep files that need protection outside the Static middleware's root directory.

---

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