CVE-2026-55677: Labstack Echo authorization bypass in static file handler

CVE-2026-55677 · Severity: high · CVSS 7.5 · Published 2026-06-26

Echo is a popular Go web framework used to build REST APIs and web applications. A mismatch in how the router and static file handler process URL-encoded slashes allows attackers to bypass authentication middleware protecting certain routes and download any file served by the application. By encoding slashes as %2F in the request URL, an attacker can access protected static files without proper authorization.

Technologies: github.com/labstack/echo/v4 (Go), github.com/labstack/echo/v5 (Go). Vendors: Go.

Quick answers

Is CVE-2026-55677 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-55677 being exploited in the wild.
How severe is CVE-2026-55677?
High severity, with a CVSS score of 7.5, published 26 June 2026.
Which products and versions are affected?
github.com/labstack/echo (Go) <= 3.3.10, SEMVER:introduced=0,last_affected=3.3.10; github.com/labstack/echo/v4 (Go) < 4.15.3, SEMVER:introduced=0,fixed=4.15.3; github.com/labstack/echo/v5 (Go) < 5.2.0, SEMVER:introduced=0,fixed=5.2.0.
Is there a fix for CVE-2026-55677?
Yes. github.com/labstack/echo/v4 (Go): upgrade to 4.15.3 or later; github.com/labstack/echo/v5 (Go): upgrade to 5.2.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-55677 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-55677?
Check whether you run github.com/labstack/echo (Go), github.com/labstack/echo/v4 (Go) or github.com/labstack/echo/v5 (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • github.com/labstack/echo/v4 (Go): upgrade to 4.15.3 or later
    go get github.com/labstack/echo/v4@v4.15.3
  • github.com/labstack/echo/v5 (Go): upgrade to 5.2.0 or later
    go get github.com/labstack/echo/v5@v5.2.0

Technical details

Echo uses req.URL.RawPath for route matching (router.go lines 798–802), which means /admin%2Fsecret.txt is treated as a single path segment and does not match the /admin/* route pattern. Meanwhile, StaticDirectoryHandler calls url.PathUnescape() before opening files (echo.go lines 559–568), converting %2F back to / and resolving admin/secret.txt on disk. An attacker can craft requests with encoded slashes to bypass route-level authentication middleware and access protected files. No authentication or special privileges are required; the exploit works over the network against any application serving static files from a broader root directory while protecting specific route prefixes with middleware. Patches are available: versions 4.15.3+ (v4 series), 5.2.0+ (v5 series), and v3.3.10 has no patch.

Affected products

  • labstack echo v3 <= 3.3.10
  • labstack echo/v4 < 4.15.3
  • labstack echo/v5 < 5.2.0

Identifiers

  • CVE-2026-55677
  • GHSA-vfp3-v2gw-7wfq
  • GO-2026-6293

Timeline

  • 2026-08-25: disclosed: GitHub Advisory published
  • 2026-06-14: patched: Patches released: echo v4.15.3 and v5.2.0; v3.x remains unpatched

References

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