Echo static file middleware route protection bypass via encoded dot-dot traversal

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.9 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS

• CVE-2026-118654: 0.35% estimated exploitation activity in the next 30 days; percentile 28.30 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Echo v5.2.0 contains a bypass of the fix for GHSA-vfp3-v2gw-7wfq. The fix rejects encoded path separators such as `%2F` and `%5C` before static file path unescaping, but two traversal forms still bypass route-level middleware protections for static files. The primary bypass uses encoded dot-dot segments. A request such as `/public/%2E%2E/admin/secret.txt` passes the encoded-separator guard, is unescaped to `public/../admin/secret.txt`, then `path.Clean` resolves it to `admin/secret.txt`. If `/admin/*` is protected by middleware but the static filesystem is mounted at `/`, the protected file is returned through the public static route. A second bypass exists when `UseEscapedPathForMatching=true`. In that mode, the router normalizes encoded separators before the static handler checks the wildcard. The handler receives a decoded wildcard with no `%` characters, so the encoded-separator guard does not run on the original encoded path.

Impact An unauthenticated attacker can…

Published by the source

28 Oct 2026, 21:04 UTC

Last modified by the source

28 Oct 2026, 21:15 UTC

Source last checked

29 Oct 2026, 06:45 UTC

1. Revision 2 · amended · 29 Oct 2026

   Amended from osv record GHSA-3pmx-cf9f-34xr

2. Revision 1 · created · 28 Oct 2026

   Published from ghsa record GHSA-3pmx-cf9f-34xr

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# Patch Next advisory brief: CVE-2026-118654

Advisory: Echo static file middleware route protection bypass via encoded dot-dot traversal
IDs: CVE-2026-118654, GHSA-3pmx-cf9f-34xr
Record: https://patchnext.com/advisories/cve-2026-118654 (revision 2, source checked 29 Oct 2026, 06:45 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/labstack/echo/v4 4.16.0; github.com/labstack/echo/v5 5.4.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/labstack/echo/v4: affected < 4.16.0; fixed in 4.16.0
- Go github.com/labstack/echo/v5: affected < 5.4.0; fixed in 5.4.0

## Suggested inspection (read-only)
- Go github.com/labstack/echo/v4: check the installed version with your package manager.
- Go github.com/labstack/echo/v5: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/labstack/echo/v4, github.com/labstack/echo/v5.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-3pmx-cf9f-34xr (GitHub-reviewed advisory GHSA-3pmx-cf9f-34xr lists affected ranges: Go github.com/labstack/echo/v5 >=0 =0 <4.16.0)
- Verified: https://osv.dev/vulnerability/GHSA-3pmx-cf9f-34xr (OSV record GHSA-3pmx-cf9f-34xr lists affected ranges: Go github.com/labstack/echo/v5 >=0 =0 <4.16.0 (fixed))

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