# CVE-2026-118262: Echo: WebSocket proxy can retain connections and handlers after client disconnect

Status: published. Published: 2026-10-28. Updated: 2026-11-03.

Echo is a Go web framework. From 4.15.0 until 4.16.1 and 5.4.1, Echo's Proxy middleware can retain a handler, copy goroutines, and network connections after a WebSocket client disconnects when the upstream keeps its connection open. The raw proxy waits for both copy directions without reliably closing the peer connection when one direction ends, including when a rejected upgrade response uses HTTP keep-alive. Repeated connections can accumulate resources and cause denial of service, depending on proxy-route accessibility, upstream behavior, and connection deadlines. This issue is fixed in 4.16.1 and 5.4.1.

## Remediation

- fix: github.com/labstack/echo/v4 (Go): OSV reports a fixed version 4.16.1. Check the advisory for supported release branches. (source: OSV GHSA-9969-6676-49h5) — https://github.com/advisories/GHSA-9969-6676-49h5
- fix: github.com/labstack/echo/v5 (Go): OSV reports a fixed version 5.4.1. Check the advisory for supported release branches. (source: OSV GHSA-9969-6676-49h5) — https://github.com/advisories/GHSA-9969-6676-49h5

## Affected products and versions

- labstack / echo: >= 4.15.0, < 4.16.1 (affected); >= 5.0.0, < 5.4.1 (affected). Source: CNA: GitHub_M
-  / github.com/labstack/echo/v4 (github.com/labstack/echo/v4): ≥ 4.15.0; < 4.16.1 (affected, semver); OSV events: introduced 4.15.0; fixed 4.16.1. Source: OSV GHSA-9969-6676-49h5
-  / github.com/labstack/echo/v5 (github.com/labstack/echo/v5): ≥ 5.0.0; < 5.4.1 (affected, semver); OSV events: introduced 5.0.0; fixed 5.4.1. Source: OSV GHSA-9969-6676-49h5

## Severity and prioritization

- CVSS 4.0: 8.2 (high); 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; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: 0.30% as of 2026-11-02; percentile 22.92%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-772

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/labstack/echo/security/advisories/GHSA-9969-6676-49h5 (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/labstack/echo/commit/1855061e572ae9dab727c811d8382f266bfbaaec (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/labstack/echo/commit/3fb0ba7e17645bb65611e2a08875d0a2f65c421f (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/labstack/echo/releases/tag/v4.16.1 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/labstack/echo/releases/tag/v5.4.1 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/advisories/GHSA-9969-6676-49h5 (OSV / GitHub Security Advisories; advisory)

- https://osv.dev/vulnerability/GHSA-9969-6676-49h5 (OSV / GitHub Security Advisories; osv)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-118262; retrieved 2026-11-03; source updated 2026-11-03

- OSV / GitHub Security Advisories: https://osv.dev/vulnerability/GHSA-9969-6676-49h5; retrieved 2026-11-03; source updated 2026-10-28

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-118262; retrieved 2026-11-03; source updated Not reported

Revision: 05f21d10ea79e4fc65b8d42efa9886fcae58fc76ce8b7322de90df357909b16a

Canonical: https://y2.dev/cve/CVE-2026-118262

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