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Advisory record · GHSA-cxf3-9h37-7rr8

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

CVSS 9.1 CriticalCriticalEPSS 0.0043 · 37th percentile

Critical, because:

  • CVSS score 9.1: 9.0 or more.

How we decide what’s critical

Published by the GitHub Advisory Database at 23 Oct 2026, 20:49 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
github.com/labstack/echo/v4Go>=4.0.0, <4.16.14.16.1
github.com/labstack/echo/v5Go>=5.0.0, <5.4.15.4.1
Identifiers
GHSA-cxf3-9h37-7rr8 · CVE-2026-118264 · GO-2026-6839
Weakness (CWE)
CWE-444 · CWE-863
Tags
Published
23 Oct 2026
Updated
5 Nov 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Echo v4 (>=4.0.0, <4.16.1) and Echo v5 (>=5.0.0, <5.4.1) Proxy middleware can forward HTTP requests to an upstream after a rejected WebSocket upgrade, bypassing route-level authentication or authorization in Echo. An attacker with access to a proxy route whose upstream rejects the upgrade without closing the connection could reach upstream resources that lack their own authorization checks. Upgrade to Echo v4.16.1 or v5.4.1; rejecting WebSocket upgrade requests before they reach affected proxy routes is an alternative workaround.

Written 1 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
9.1 Critical 4.0 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0043, the 37th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 28 Oct 2026, 19:17 UTC Confirmed by NVD
  2. 31 Oct 2026, 14:11 UTC First seen by agentprime
  3. 31 Oct 2026, 14:11 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.