# Authentication and extension bypass in Faye

Advisory record · `GHSA-qpg4-4w7w-2mq5`

- **Identifiers:** `GHSA-qpg4-4w7w-2mq5` · `CVE-2020-11020`
- **State:** Confirmed
- **Severity:** CVSS 8.5 High
- **Critical:** No
- **Weakness (CWE):** [CWE-287](https://cwe.mitre.org/data/definitions/287.html)
- **Tags:** [Authentication bypass](https://agentprime.io/advisories/tag/auth-bypass.md)
- **Published:** 29 Apr 2020
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 29 Apr 2020, 17:41 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `faye` (RubyGems): affected `>=0.5.0, <1.0.4 || >=1.1.0, <1.1.3 || >=1.2.0, <1.2.5`; fixed in `1.0.4`, `1.1.3`, `1.2.5`

## Machine-written summary

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

> Faye for RubyGems, versions from 0.5.0 up to 1.0.4, from 1.1.0 up to 1.1.3, and from 1.2.0 up to 1.2.5, is affected. A client that can connect to the server can send messages to meta channels such as /meta/subscribe with extra path segments appended, which the server still processes as exact matches, bypassing access checks in server-side extensions. Upgrade to Faye 1.0.4, 1.1.3, or 1.2.5. If upgrading is not possible, make extensions check that the channel begins with the expected meta channel name.

Written 8 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

- 8.5 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.016, the 75th percentile, on 10 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 15:16 UTC: First seen by agentprime
- 31 Oct 2026, 15:16 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-qpg4-4w7w-2mq5)

## Sources

- [GitHub Advisory Database: GHSA-qpg4-4w7w-2mq5](https://github.com/advisories/GHSA-qpg4-4w7w-2mq5)
- [OSV: GHSA-qpg4-4w7w-2mq5](https://osv.dev/vulnerability/GHSA-qpg4-4w7w-2mq5)
- <https://github.com/faye/faye/security/advisories/GHSA-qpg4-4w7w-2mq5>
- <https://nvd.nist.gov/vuln/detail/CVE-2020-11020>
- <https://github.com/faye/faye/commit/65d297d341b607f3cb0b5fa6021a625a991cc30e>
- <https://github.com/faye/faye>
- <https://github.com/rubysec/ruby-advisory-db/blob/master/gems/faye/CVE-2020-11020.yml>

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-qpg4-4w7w-2mq5>, 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-qpg4-4w7w-2mq5/>. Everything for agents: <https://agentprime.io/llms.txt>.