# Phoenix transports do not limit channel joins per connection, enabling process-exhaustion denial of service

Advisory record · `GHSA-6983-jfq8-485w`

- **Identifiers:** `GHSA-6983-jfq8-485w` · `CVE-2026-56811` · `EEF-CVE-2026-56811`
- **State:** Confirmed
- **Severity:** CVSS 8.7 High
- **Critical:** No
- **Weakness (CWE):** [CWE-770](https://cwe.mitre.org/data/definitions/770.html)
- **Tags:** [Denial of service](https://agentprime.io/advisories/tag/dos.md)
- **Published:** 7 Jul 2026
- **Updated:** 24 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 7 Jul 2026, 15:09 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `phoenix` (Hex): affected `>=0.11.0, <1.5.15 || >=1.6.0-rc.0, <1.6.17 || >=1.7.0-rc.0, <1.7.24 || >=1.8.0-rc.0, <1.8.9`; fixed in `1.5.15`, `1.6.17`, `1.7.24`, `1.8.9`

## 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

- 8.7 High, CVSS 4.0: `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`, from CNA (EEF)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0077, the 55th percentile, on 6 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 15:25 UTC: First seen by agentprime
- 31 Oct 2026, 15:25 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/EEF-CVE-2026-56811)

## Sources

- [GitHub Advisory Database: GHSA-6983-jfq8-485w](https://github.com/advisories/GHSA-6983-jfq8-485w)
- [OSV: GHSA-6983-jfq8-485w](https://osv.dev/vulnerability/GHSA-6983-jfq8-485w)
- <https://github.com/phoenixframework/phoenix/security/advisories/GHSA-6983-jfq8-485w>
- <https://cna.erlef.org/cves/CVE-2026-56811.html>
- <https://github.com/phoenixframework/phoenix/commit/14a297e88023cb280a577962a49a0bbdeef9f4eb>
- <https://github.com/phoenixframework/phoenix/commit/c498ba8cf49f6accbbd0c643a5340b58db891218>
- <https://github.com/phoenixframework/phoenix/commit/d19ca0a8d9f82c130b7ed339b9f033433e2dea5e>
- <https://github.com/phoenixframework/phoenix/commit/a612100cd8a4279091abc1a2ef8fb98a6d01c0a1>
- <https://github.com/phoenixframework/phoenix/commit/16e295d2fccab185d1292322e2bee5d46c725c8a>
- <https://hex.pm/packages/phoenix>

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 (<https://api.agentprime.io/mcp>), 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: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-6983-jfq8-485w>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-6983-jfq8-485w/>. Everything for agents: <https://agentprime.io/llms.txt>.