Echo: WebSocket proxy can retain connections and handlers after client disconnect

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.2 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-118262: 0.30% estimated exploitation activity in the next 30 days; percentile 22.97 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact Echo's Proxy middleware could retain a handler, copy goroutines and network connections after a WebSocket client disconnected if the upstream kept its connection open. The raw proxy waited for both copy directions to finish without reliably closing the other connection when one direction ended. Rejected upgrade responses with HTTP keep-alive were one way to trigger this behavior. Repeated connections can accumulate resources and cause denial of service. The impact depends on the proxy route's accessibility, upstream behavior and configured connection deadlines. This is a medium-severity resource-retention issue; no confidentiality or integrity impact is claimed.

Affected versions and patch Affected versions are v4.15.0 through v4.16.0 and v5.0.0 through v5.4.0. The regression was introduced by commit e2133320c7, merged in #2852. Upgrade to v4.16.1 or v5.4.1.…

Published by the source

23 Oct 2026, 20:50 UTC

Last modified by the source

28 Oct 2026, 19:15 UTC

Source last checked

29 Oct 2026, 06:45 UTC

1. Revision 6 · amended · 29 Oct 2026

   Amended from osv record GHSA-9969-6676-49h5

2. Revision 5 · amended · 28 Oct 2026

   Amended from ghsa record GHSA-9969-6676-49h5

3. Revision 4 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-9969-6676-49h5

4. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-9969-6676-49h5

5. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

6. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-9969-6676-49h5

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# Patch Next advisory brief: CVE-2026-118262

Advisory: Echo: WebSocket proxy can retain connections and handlers after client disconnect
IDs: CVE-2026-118262, GHSA-9969-6676-49h5
Record: https://patchnext.com/advisories/ghsa-9969-6676-49h5 (revision 6, source checked 29 Oct 2026, 06:45 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/labstack/echo/v4 4.16.1; github.com/labstack/echo/v5 5.4.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/labstack/echo/v4: affected >= 4.15.0, < 4.16.1; fixed in 4.16.1
- Go github.com/labstack/echo/v5: affected >= 5.0.0, < 5.4.1; fixed in 5.4.1

## Suggested inspection (read-only)
- Go github.com/labstack/echo/v4: check the installed version with your package manager.
- Go github.com/labstack/echo/v5: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/labstack/echo/v4, github.com/labstack/echo/v5.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-9969-6676-49h5 (OSV record GHSA-9969-6676-49h5 lists affected ranges: Go github.com/labstack/echo/v4 >=4.15.0 =5.0.0 <5.4.1 (fixed))
- Verified: https://github.com/advisories/GHSA-9969-6676-49h5 (GitHub-reviewed advisory GHSA-9969-6676-49h5 lists affected ranges: Go github.com/labstack/echo/v4 >=4.15.0 =5.0.0 <5.4.1)

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