Missing TLS certificate verification in faye-websocket

Exploitation

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

CVSS

8.0 · CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N

EPSS

• CVE-2020-15133: 0.92% estimated exploitation activity in the next 30 days; percentile 60.28 (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.

The Faye::WebSocket::Client class uses the [EM::Connection#starttls][1] method in [EventMachine][2] to implement the TLS handshake whenever a wss: URL is used for the connection. This method does not implement certificate verification by default, meaning that it does not check that the server presents a valid and trusted TLS certificate for the expected hostname. That means that any wss: connection made using this library is vulnerable to a man-in-the-middle attack, since it does not confirm the identity of the server it is connected to. This has been a requested feature in EventMachine for many years now; see for example [#275][3], [#378][4], and [#814][5]. In June 2020, [em-http-request][6] published an [advisory][7] related to this problem and fixed it by [implementing TLS verification][8] in their own codebase; although EventMachine does not implement certificate verification itself, it provides an extension point for the caller to implement it, called [sslverifypeer][9]. Based…

Published by the source

31 Jul 2020, 17:40 UTC

Last modified by the source

16 May 2023, 16:01 UTC

Source last checked

26 Oct 2026, 15:47 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-2v5c-755p-p4gv

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# Patch Next advisory brief: CVE-2020-15133

Advisory: Missing TLS certificate verification in faye-websocket
IDs: CVE-2020-15133, GHSA-2v5c-755p-p4gv
Record: https://patchnext.com/advisories/cve-2020-15133 (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 8.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: faye-websocket 0.11.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems faye-websocket: affected < 0.11.0; fixed in 0.11.0

## Suggested inspection (read-only)
- RubyGems faye-websocket: 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-websocket.
- 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-2v5c-755p-p4gv (GitHub-reviewed advisory GHSA-2v5c-755p-p4gv lists affected ranges: RubyGems faye-websocket >=0 <0.11.0)

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