GHSA-XWQ5-6CQP-VX96

Vulnerability from github – Published: 2026-10-28 21:04 – Updated: 2026-10-28 21:04
VLAI
Summary
Echo has a Static Middleware Double-Unescape Path Traversal
Details

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:

// 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

// 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.

Severity
5.9 (Medium)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/labstack/echo/v5"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "5.2.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/labstack/echo/v4"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.15.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-118655"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-174"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-10-28T21:04:39Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "## Summary\n\nCommit a9ede66a (PR #3006, issue #2599) silently fixed a path traversal vulnerability in the Echo web framework\u0027s static file middleware.\n\n## Vulnerability\n\nThe static middleware double-unescaped URL paths. Go\u0027s net/http already decodes Request.URL.Path, but middleware/static.go unconditionally called url.PathUnescape() again:\n\n```go\n// BEFORE (vulnerable)\npathUnescape := true\n```\n\nThis 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.\n\n## Fix\n```go\n// AFTER (fixed)\npathUnescape := false\n```\n\nThe commit\u0027s test TestStatic_percentEncodedTraversalIsBlocked explicitly verifies traversal vectors are blocked.\n\n## Impact\nArbitrary file read from server filesystem via percent-encoded path traversal.\n\n## References\n- Fix: https://github.com/labstack/echo/commit/a9ede66a\n- Issue: https://github.com/labstack/echo/issues/2599\n- PR: https://github.com/labstack/echo/pull/3006\n\n## Patches\n\nFixed 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.\n\n## Workarounds\n\nKeep files that need protection outside the Static middleware\u0027s root directory.",
  "id": "GHSA-xwq5-6cqp-vx96",
  "modified": "2026-10-28T21:04:39Z",
  "published": "2026-10-28T21:04:39Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/labstack/echo/security/advisories/GHSA-xwq5-6cqp-vx96"
    },
    {
      "type": "WEB",
      "url": "https://github.com/labstack/echo/issues/2599"
    },
    {
      "type": "WEB",
      "url": "https://github.com/labstack/echo/pull/3006"
    },
    {
      "type": "WEB",
      "url": "https://github.com/labstack/echo/commit/a9ede66a5a7196411131beb1ee801e75bbaf7ac6"
    },
    {
      "type": "WEB",
      "url": "https://github.com/labstack/echo/commit/c3fa2a27ff92b2b8db360de614f999ef1da24725"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/labstack/echo"
    },
    {
      "type": "WEB",
      "url": "https://github.com/labstack/echo/releases/tag/v4.15.3"
    },
    {
      "type": "WEB",
      "url": "https://github.com/labstack/echo/releases/tag/v5.2.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Echo has a Static Middleware Double-Unescape Path Traversal"
}



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