# Echo: WebSocket proxy can retain connections and handlers after client disconnect Advisory record · `GHSA-9969-6676-49h5` - **Identifiers:** `GHSA-9969-6676-49h5` · `CVE-2026-118262` · `GO-2026-6838` - **State:** Confirmed - **Severity:** CVSS 8.2 High - **Critical:** No - **Weakness (CWE):** [CWE-772](https://cwe.mitre.org/data/definitions/772.html) - **Tags:** [Denial of service](https://agentprime.io/advisories/tag/dos.md) - **Published:** 23 Oct 2026 - **Updated:** 5 Nov 2026 - **Reviewed by a person:** No Published by the GitHub Advisory Database at 23 Oct 2026, 20:50 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. ## Affected packages - `github.com/labstack/echo/v4` (Go): affected `>=4.15.0, <4.16.1`; fixed in `4.16.1` - `github.com/labstack/echo/v5` (Go): affected `>=5.0.0, <5.4.1`; fixed in `5.4.1` ## Machine-written summary Summary written by Claude Haiku from the source advisory. Not reviewed by a person. > Echo's Proxy middleware in github.com/labstack/echo/v4 (4.15.0 through 4.16.0) and github.com/labstack/echo/v5 (5.0.0 through 5.4.0) can keep handlers, goroutines and network connections alive after a WebSocket client disconnects, if the upstream keeps its side open. An attacker who can reach a WebSocket proxy route can repeat connections to accumulate resources and cause a denial of service. Upgrade to v4.16.1 or v5.4.1. Until then, disable WebSocket proxy routes or apply bounded connection lifetimes and resource limits. 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 - 8.2 High, CVSS 4.0: `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`, from CNA (GitHub_M) - **CISA KEV:** Not listed. - **EPSS:** 0.0030, the 23rd percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days. ## Timeline - 28 Oct 2026, 19:00 UTC: [Confirmed by the CVE List](https://www.cve.org/CVERecord?id=CVE-2026-118262) - 28 Oct 2026, 19:17 UTC: [Confirmed by NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-118262) - 31 Oct 2026, 14:11 UTC: First seen by agentprime - 31 Oct 2026, 14:11 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-9969-6676-49h5) ## Sources - [GitHub Advisory Database: GHSA-9969-6676-49h5](https://github.com/advisories/GHSA-9969-6676-49h5) - [OSV: GHSA-9969-6676-49h5](https://osv.dev/vulnerability/GHSA-9969-6676-49h5) - - - - - - 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. ## Check whether this affects you A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet. - With the agentprime MCP server (), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: - In a browser: reads your lockfile in the browser, never uploading it. - Whether it touches your code, with file and line: the Claude Code plugin, - As JSON: , or `POST https://api.agentprime.io/v1/match` with your packages () --- The web page: . Everything for agents: .