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CVE-2026-118264critical9.1

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

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.

Source excerpt · OSV
Applies when

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.

What to do

Upgrade to v4.16.1 or v5.4.1.

OSV guidance

Affected packages

Start with the recorded fix for your release branch. Check your installed version and test compatibility before upgrading. Fixing this advisory does not rule out other vulnerabilities in the release.

Affected products

Vendor version evidence. Product records are separate from automatic dependency matching.

labstack · GitHub_M

echo

2 ranges
GitHub_M version evidence

Compare with this publisher’s ranges. This does not inspect your installation.

affected

>= 4.0.0, < 4.16.1

>= 5.0.0, < 5.4.1

unaffected

unknown

Other versions: unknown

Original source 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 or 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, v5.

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.

Inside the record

Evidence available

Package identity
Version evidence
Remediation guidance · not supplied
Weakness classification
Additional publishers

Describes the evidence in this view, not whether the product is safe.

Original records

CVE-2026-118264

View the latest unmodified CVE JSON from the official source. It may be newer than this imported page.

cve.new JSON →

Underlying weaknesses

The source’s classification of what caused the vulnerability.

CWE-444 ↗

CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

GitHub_M

Related →
CWE-863 ↗

CWE-863: Incorrect Authorization

GitHub_M

Related →
Contributing organizations · 2
GitHub_M

Assigning organization

2026-10-28
CISA-ADP

Additional data publisher

2026-10-30

What changed

Follow changes
  1. CVE · CVE-2026-118264

    Observed 2026-10-30T19:39:45.793Z · upstream updated 2026-10-30T19:21:07.156Z

    Prioritization updated

    before

    []

    after

    [
  {
    "source": "CISA-ADP",
    "type": "SSVC",
    "role": "CISA Coordinator",
    "timestamp": "2026-10-30T19:20:57.948930Z",
    "decisions": [
      {
        "name": "Exploitation",
        "value": "none"
      },
      {
        "name": "Automatable",
        "value": "yes"
      },
      {
        "name": "Technical Impact",
        "value": "total"
      }
    ]
  }
]

Large field values are marked as truncated previews. Original source snapshots remain retained.

Showing up to 50 most recent observed changes.

References

6 sources
github.com/labstack/echo/security/advisories/GHSA-cxf3-9h37-7rr8
Security advisoryGitHub_M
github.com/labstack/echo/commit/1855061e572ae9dab727c811d8382f266bfbaaec
PatchGitHub_M
github.com/labstack/echo/commit/3fb0ba7e17645bb65611e2a08875d0a2f65c421f
PatchGitHub_M
github.com/labstack/echo
Source reference
github.com/labstack/echo/releases/tag/v4.16.1
Release notesGitHub_M
github.com/labstack/echo/releases/tag/v5.4.1
Release notesGitHub_M