Authentication and extension bypass in Faye

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.5 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N

EPSS

• CVE-2020-11020: 1.57% estimated exploitation activity in the next 30 days; percentile 75.44 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

On 20 April 2020 it was reported to me that the potential for authentication bypass exists in [Faye][1]'s extension system. This vulnerability has existed in the Node.js and Ruby versions of the server since version 0.5.0, when extensions were first introduced, in July 2010. It is patched in versions 1.0.4, 1.1.3 and 1.2.5, which we are releasing today. The vulnerability allows any client to bypass checks put in place by server-side extensions, by appending extra segments to the message channel. For example, the Faye [extension docs][2] suggest that users implement access control for subscriptions by checking incoming messages for the /meta/subscribe channel, for example: A bug in the server's code for recognising the special /meta/ channels, which trigger connection and subscription events, means that a client can bypass this check by sending a message to /meta/subscribe/x rather than /meta/subscribe: This message will not be checked by the above extension, as it checks the…

Published by the source

29 Apr 2020, 17:41 UTC

Last modified by the source

16 May 2023, 15:51 UTC

Source last checked

26 Oct 2026, 15:47 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-qpg4-4w7w-2mq5

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# Patch Next advisory brief: CVE-2020-11020

Advisory: Authentication and extension bypass in Faye
IDs: CVE-2020-11020, GHSA-qpg4-4w7w-2mq5
Record: https://patchnext.com/advisories/cve-2020-11020 (revision 1, source checked 26 Oct 2026, 15:47 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: faye 1.2.5, 1.1.3, 1.0.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems faye: affected >= 0.5.0, < 1.0.4; >= 1.1.0, < 1.1.3; >= 1.2.0, < 1.2.5; fixed in 1.0.4, 1.2.5, 1.1.3

## Suggested inspection (read-only)
- RubyGems faye: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on faye.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-qpg4-4w7w-2mq5 (GitHub-reviewed advisory GHSA-qpg4-4w7w-2mq5 lists affected ranges: RubyGems faye >=0.5.0 =1.1.0 =1.2.0 <1.2.5)

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