How severe is GHSA-9969-6676-49h5?

No CVSS score has been assigned to GHSA-9969-6676-49h5 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by GHSA-9969-6676-49h5?

GHSA-9969-6676-49h5 affects the following packages: github.com/labstack/echo/v4 (Go), github.com/labstack/echo/v5 (Go). Ecosystems affected: Go.

How do I fix GHSA-9969-6676-49h5?

Update github.com/labstack/echo/v4 to 4.16.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-9969-6676-49h5 is resolved across your whole dependency graph.

How do I detect GHSA-9969-6676-49h5 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/labstack/echo/v4, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate GHSA-9969-6676-49h5 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is GHSA-9969-6676-49h5 actively exploited in the wild?

No public exploit code has been indexed for GHSA-9969-6676-49h5 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

When was GHSA-9969-6676-49h5 published, and has it been updated?

GHSA-9969-6676-49h5 was published on October 23, 2026 and was last updated on October 23, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

Not in CISA KEV

Echo: WebSocket proxy can retain connections and handlers after client disconnectGHSA-9969-6676-49h5

Fix: labstack/echo@1855061

GHSA-9969-6676-49h5 is a security vulnerability in github.com/labstack/echo/v4. A fix is available for github.com/labstack/echo/v4 — see the affected versions and patch details below.

Published

Oct 23, 2026

Updated

Oct 23, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Oct 23, 2026 · OSV.dev, FIRST.org (EPSS)

Real-World Exposure

2 pkgs affected

🐹github.com/labstack/echo/v4🐹github.com/labstack/echo/v5

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

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. The patch uses Go's HTTP reverse proxy, preserves ordinary HTTP handling for rejected upgrades, and closes both sides of a WebSocket tunnel when either direction ends. It also covers an upstream that receives client EOF but deliberately keeps its side open.

Fix commits: v4, v5.

Workarounds

Disable WebSocket proxy routes until upgrading, or apply bounded connection lifetimes and resource limits at the frontend and upstream. Server idle timeouts alone may not cover hijacked WebSocket connections.

Credits

Reported by @irisitymichaelgrundberg.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/labstack/echo/v4`	≥ 4.15.0&&< 4.16.1	4.16.1`go get github.com/labstack/echo/v4@v4.16.1`
🐹Go	`github.com/labstack/echo/v5`	≥ 5.0.0&&< 5.4.1	5.4.1`go get github.com/labstack/echo/v5@v5.4.1`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/labstack/echo/v4, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/labstack/echo/v4 to 4.16.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-9969-6676-49h5 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

## 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-sev

O3 Security · Impact-Aware SCA

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