# CVE-2026-118264: Echo Proxy middleware WebSocket upgrade validation bypass

Source: https://junglewise.ai/threats/cve-2026-118264-echo-is-a-go-web-framework-from-4-0-0-until-4-16-1-and-5-4-1  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-28. Updated: 2026-10-28  
License: CC BY 4.0 with a link back

CVE-2026-118264 · Severity: info · Published 2026-10-28

Echo is a Go web framework used to build HTTP services and APIs. The Proxy middleware component can be bypassed when handling WebSocket upgrade requests: if an upstream server rejects the upgrade, subsequent HTTP requests on that connection are sent directly to the upstream without passing through Echo's authentication or authorization checks. An attacker with access to a proxy route could exploit this to access protected resources on the backend server.

Technologies: [github.com/labstack/echo/v4 (Go)](https://junglewise.ai/threats/technologies/github-com-labstack-echo-v4), [github.com/labstack/echo/v5 (Go)](https://junglewise.ai/threats/technologies/github-com-labstack-echo-v5), [Labstack Echo](https://junglewise.ai/threats/technologies/labstack-echo). Vendors: [Go](https://junglewise.ai/threats/vendors/go), [Labstack](https://junglewise.ai/threats/vendors/labstack).

## Quick answers

**Is CVE-2026-118264 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-118264 being exploited in the wild.

**How severe is CVE-2026-118264?** Informational severity, published 28 October 2026.

**Which products and versions are affected?** github.com/labstack/echo/v4 (Go) SEMVER:introduced=4.0.0,fixed=4.16.1; github.com/labstack/echo/v5 (Go) SEMVER:introduced=5.0.0,fixed=5.4.1; Labstack Echo 4.0.0 to 4.16.0, 5.0.0 to 5.4.0.

**Is there a fix for CVE-2026-118264?** Yes. github.com/labstack/echo/v4 (Go): upgrade to 4.16.1 or later; github.com/labstack/echo/v5 (Go): upgrade to 5.4.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-118264 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-118264?** Check whether you run github.com/labstack/echo/v4 (Go), github.com/labstack/echo/v5 (Go) or Labstack Echo 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 4.16.1 or later

  ```sh
  go get github.com/labstack/echo/v4@v4.16.1
  ```

- github.com/labstack/echo/v5 (Go): upgrade to 5.4.1 or later

  ```sh
  go get github.com/labstack/echo/v5@v5.4.1
  ```


## Technical details

The Proxy middleware in Echo versions 4.0.0–4.16.0 and 5.0.0–5.4.0 fail to validate that an upstream accepted a WebSocket upgrade before establishing a tunnel. If the upstream returns a keep-alive HTTP response rejecting the upgrade, the middleware creates a raw tunnel for subsequent requests without routing them through Echo's middleware chain. This allows bypass of route-level authentication or authorization, provided the attacker can craft a rejected-upgrade scenario and the target backend lacks independent authorization checks.

## Affected products

- labstack Echo 4.0.0 to 4.16.0, 5.0.0 to 5.4.0

## Identifiers

- CVE-2026-118264
- GHSA-cxf3-9h37-7rr8
- GO-2026-6839

## Timeline

- 2026-10-28: disclosed

## References

- [https://github.com/labstack/echo/commit/1855061e572ae9dab727c811d8382f266bfbaaec](https://github.com/labstack/echo/commit/1855061e572ae9dab727c811d8382f266bfbaaec)
- [https://github.com/labstack/echo/commit/3fb0ba7e17645bb65611e2a08875d0a2f65c421f](https://github.com/labstack/echo/commit/3fb0ba7e17645bb65611e2a08875d0a2f65c421f)

## Related threats

- [Echo web framework arbitrary URI scheme redirect](https://junglewise.ai/threats/cve-2026-118658-echo-is-a-go-web-framework-prior-to-4-15-2-and-5-1-1-context)
- [Echo Go web framework scheme header spoofing and HSTS bypass](https://junglewise.ai/threats/cve-2026-118657-echo-is-a-go-web-framework-prior-to-4-16-0-and-5-4-0-context)
- [Echo open redirect in sanitizeURI with trailing slash redirect](https://junglewise.ai/threats/cve-2026-118656-echo-is-a-go-web-framework-prior-to-4-16-0-and-5-4-0-sanitizeuri)
- [Echo path traversal via double URL encoding in Static middleware](https://junglewise.ai/threats/cve-2026-118655-echo-is-a-go-web-framework-prior-to-4-15-3-and-5-2-0-middleware)
- [Echo path traversal in static file handlers via dot segment normalization](https://junglewise.ai/threats/cve-2026-118654-echo-is-a-go-web-framework-prior-to-4-16-0-and-5-4-0-echo-s)