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Vulnerabilities

Security fix · GHSA-cxf3-9h37-7rr8

Echo: Rejected WebSocket upgrades can bypass Echo route-level access controls

Published Oct 23, 2026 · catalog updated Oct 23, 2026 · Echo: Rejected WebSocket upgrades

Last checked Oct 28, 2026, 11 days ago.

Open the advisory

Exploitation likelihood is not on this record for GHSA-cxf3-9h37-7rr8. A missing EPSS score is not a low risk. Compare Echo: Rejected WebSocket upgrades with the linked advisory before you change production.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Echo: Rejected WebSocket upgrades).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
  • EPSS is missing. A missing score is not a low risk.
Severity
Critical—
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
Awaiting synchronization with FIRST
Remediation
Advisory link
Affected products
Go github.com/labstack/echo/v4 · Go github.com/labstack/echo/v5

## 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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • Go github.com/labstack/echo/v44.0.0 → 4.16.1
  • Go github.com/labstack/echo/v55.0.0 → 5.4.1

How to fix GHSA-cxf3-9h37-7rr8

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

Exploitation likelihood is not on this record for GHSA-cxf3-9h37-7rr8. A missing EPSS score is not a low risk. Compare Echo: Rejected WebSocket upgrades with the linked advisory before you change production.

Which versions are affected?

Compare what you have installed with 4.0.0 → 4.16.1, 5.0.0 → 5.4.1. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-444: HTTP Request Smuggling; CWE-863: Incorrect Authorization. EPSS is not on this record yet. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 23, 2026 · GitHub Advisory Database

    Detected

    ## 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 middlew

  2. Oct 23, 2026 · GitHub Advisory Database

    Fix available

    github.com/labstack/echo/v4 fixed in 4.16.1; github.com/labstack/echo/v5 fixed in 5.4.1

  3. Oct 23, 2026 · GitHub Advisory Database

    Fix available

    github.com/labstack/echo/v4 fixed in 4.16.1

  4. Oct 23, 2026 · GitHub Advisory Database

    Fix available

    github.com/labstack/echo/v5 fixed in 5.4.1

  5. Oct 23, 2026 · GitHub Advisory Database

    Updated

    ## 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 middlew

Sources

References

Freshness

Last verified in this catalog Oct 23, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • Go Vulnerability DatabaseOct 28, 2026
  • GitHub Advisory DatabaseOct 26, 2026
  • OpenSSF OSV / OSV ScannerOct 26, 2026