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High, CVSS 7.5amended

Echo: Encoded slash (%2F) bypasses route-level protection and exposes static files

CVE-2026-55677GHSA-vfp3-v2gw-7wfq

What to do

Partial vendor fix. Follow the primary source's mitigation guidance and check back for a fix.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • Go github.com/labstack/echo/v4

    Affected
    < 4.15.3
    Fixed in
    4.15.3

  • Go github.com/labstack/echo/v5

    Affected
    < 5.2.0
    Fixed in
    5.2.0

  • Go github.com/labstack/echo

    Affected
    <= 3.3.10
    Fixed in
    no fixed version recorded

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
EPSS
  • CVE-2026-55677: 0.52% estimated exploitation activity in the next 30 days; percentile 44.20 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary Echo's router and static file handler disagree on URL path decoding. The router matches routes using the raw encoded path (preserving %2F as-is), while StaticDirectoryHandler unescapes %2F to / before resolving filesystem paths. This allows an attacker to bypass route-level access controls and read static files without authorization. Details Root cause 1 — router.go lines 798-802: The router uses req.URL.RawPath for route matching when useEscapedPathForRouting is false (the default). This means /admin%2Fsecret.txt is treated as a single path segment and does NOT match the /admin/ route pattern. Root cause 2 — echo.go lines 559-568: StaticDirectoryHandler calls url.PathUnescape() on the path parameter before opening files. This converts %2F back to /, resolving admin/secret.txt on disk. PoC (Screenshot) Sample: <img width="1291" height="970" alt="image" src="https://github.com/user-attachments/assets/0bc58059-3e6d-4678-ab25-a5c79b006738" / 403: <img width="526" height="194"…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-vfp3-v2gw-7wfq

  2. Revision 2 · amended ·

    Amended from osv record GO-2026-6293

  3. Revision 1 · created ·

    Published from osv record GHSA-vfp3-v2gw-7wfq

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-55677

Advisory: Echo: Encoded slash (%2F) bypasses route-level protection and exposes static files
IDs: CVE-2026-55677, GHSA-vfp3-v2gw-7wfq
Record: https://patchnext.com/advisories/cve-2026-55677 (revision 3, source checked 26 Oct 2026, 15:28 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: github.com/labstack/echo/v4 4.15.3; github.com/labstack/echo/v5 5.2.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/labstack/echo/v4: affected < 4.15.3; fixed in 4.15.3
- Go github.com/labstack/echo/v5: affected < 5.2.0; fixed in 5.2.0
- Go github.com/labstack/echo: affected <= 3.3.10

## 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.
- Go github.com/labstack/echo: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## 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, github.com/labstack/echo.
- 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://osv.dev/vulnerability/GHSA-vfp3-v2gw-7wfq (OSV record GHSA-vfp3-v2gw-7wfq lists affected ranges: Go github.com/labstack/echo/v5 >=0 =0 =0 <=3.3.10)
- Verified: https://osv.dev/vulnerability/GO-2026-6293 (OSV record GO-2026-6293 lists affected ranges: Go github.com/labstack/echo/v4 >=0 =0 <5.2.0 (fixed))
- Verified: https://github.com/advisories/GHSA-vfp3-v2gw-7wfq (GitHub-reviewed advisory GHSA-vfp3-v2gw-7wfq lists affected ranges: Go github.com/labstack/echo/v5 >=0 =0 =0 <=3.3.10)

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