GHSA-cxf3-9h37-7rr8
Echo: Rejected WebSocket upgrades can bypass Echo route-level access controls
- Risk score
- 65/100
- CVSS
- 9.1 v4.0
- Published
- 23 Oct 2026
Open in the live forecast Today's forecast
What to know
- What it is
- Echo's Proxy middleware selected a raw tunnel when the client requested a WebSocket upgrade, before validating whether the configured upstream accepted it. If the upstream returned an ordinary HTTP response and kept the connection alive, subsequent HTTP requests on that connection were forwarded directly to the same u…
- Affected
- github.com/labstack/echo/v4 (go) >= 4.0.0, < 4.16.1; github.com/labstack/echo/v5 (go) >= 5.0.0, < 5.4.1
- Fix
- Upgrade github.com/labstack/echo/v4 to 4.16.1; github.com/labstack/echo/v5 to 5.4.1 or later.
- Exploitation
- No known exploitation
Story map
At a glance
github.com/labstack/echo/v4: Amber, patch this week. Echo's Proxy middleware selected a raw tunnel when the client requested a WebSocket upgrade, before validating whether the configured upstream accepted it. If the upstream returned an ordinary HTTP response and kept the connection alive, subsequent HTTP requests on that connection were forwarded directly to the same u…
The flaws
- GHSA-cxf3-9h37-7rr8: Echo: Rejected WebSocket upgrades can bypass Echo route-level access controls (CVSS 9.1)
- GHSA-9969-6676-49h5: Echo: WebSocket proxy can retain connections and handlers after client disconnect (CVSS 8.2)
- GHSA-h7wr-284f-5qvc: Echo: Decompress permits unbounded gzip expansion in v4 (CVSS 8.2)
- GHSA-f48p-c9v4-h7xv: Echo: BodyDump captures request and response bodies without size limits in v4 (CVSS 8.2)
The fix
Fix: Upgrade github.com/labstack/echo/v4 to 4.16.1; github.com/labstack/echo/v5 to 5.4.1 or later.
Who is exposed: github.com/labstack/echo/v4 (go) >= 4.0.0, < 4.16.1; github.com/labstack/echo/v5 (go) >= 5.0.0, < 5.4.1
Where it stands
- No known exploitation
Connects to
- Same weakness: CWE-444 (CWE-444). 28 other warnings in 30 days
Why it is Amber
- CVSS 9.1 critical
- Remotely exploitable without logging in
- On your watchlist: Go
Affected packages
| Package | Ecosystem | Vulnerable | Fixed in |
|---|---|---|---|
| github.com/labstack/echo/v4 | go | >= 4.0.0, < 4.16.1 | 4.16.1 |
| github.com/labstack/echo/v5 | go | >= 5.0.0, < 5.4.1 | 5.4.1 |
References
- https://github.com/advisories/GHSA-cxf3-9h37-7rr8
- https://github.com/labstack/echo/security/advisories/GHSA-cxf3-9h37-7rr8
- https://github.com/labstack/echo/commit/1855061e572ae9dab727c811d8382f266bfbaaec
- https://github.com/labstack/echo/commit/3fb0ba7e17645bb65611e2a08875d0a2f65c421f
- https://github.com/labstack/echo/releases/tag/v4.16.1
- https://github.com/labstack/echo/releases/tag/v5.4.1
- https://github.com/advisories/GHSA-cxf3-9h37-7rr8
Original description
## Impact Echo's Proxy middleware selected a raw tunnel when the client requested a WebSocket upgrade, before validating whether the configured upstream accepted it. If the upstream returned an ordinary HTTP response and kept the connection alive, subsequent HTTP requests on that connection were forwarded directly to the same upstream without passing through Echo's router or route-specific middleware. This can bypass authentication or authorization enforced only at Echo's routes. Exploitation requires an accessible proxy route, an upstream that rejects the upgrade without closing the connection, and a target resource on that upstream without independent authorization. The issue does not provide arbitrary-host proxying or bypass the upstream's own authentication. ## Affected versions and patch The raw proxy implementation is present throughout the v4 and v5 release lines up to v4.16.0 and v5.4.0. Runtime reproductions confirmed v4.15.0, v4.16.0, v5.0.0 and v5.4.0; source history also shows the missing upgrade-response validation in v4.0.0. Upgrade to [v4.16.1](https://github.com/labstack/echo/releases/tag/v4.16.1) or [v5.4.1](https://github.com/labstack/echo/releases/tag/v5.4.1). The patch routes WebSocket upgrades through Go's HTTP reverse proxy and enters a tunnel only after a valid upstream upgrade response. Rejected upgrades remain ordinary HTTP requests. Fix commits: [v4](https://github.com/labstack/echo/commit/3fb0ba7e17645bb65611e2a08875d0a2f65c421f), [v5](https://github.com/labstack/echo/commit/1855061e572ae9dab727c811d8382f266bfbaaec). ## Workarounds Reject WebSocket upgrade requests before they reach affected Echo proxy routes, or enforce authorization independently at every upstream resource. Merely returning a non-101 response from the upstream does not prevent the vulnerable raw tunnel. ## Credits Reported by @Duodum.
Last activity 23 Oct 2026. Patch Forecast updates every hour.