What’s Vulnerable › Vulnerabilities

CVE-2020-15133: Missing TLS certificate verification in Faye Websocket

• Severity: high (CVSS 8.7 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.9% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2020-07-31 · updated 2026-06-17
• Weakness: CWE-295

Description

In faye-websocket before version 0.11.0, there is a lack of certification validation in TLS handshakes. The `Faye::WebSocket::Client` class uses the `EM::Connection#start_tls` method in EventMachine 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. For further background information on this issue, please see the referenced GitHub Advisory. Upgrading `faye-websocket` to v0.11.0 is recommended.

Affected products

• faye-websocket: before 0.11.0 — fixed in 0.11.0

How to fix

Upgrade to a fixed version: faye-websocket 0.11.0. Check the vendor advisory for mitigations.

References

• https://blog.jcoglan.com/2020/07/31/missing-tls-verification-in-faye/
• https://github.com/faye/faye-websocket-ruby/security/advisories/GHSA-2v5c-755p-p4gv
• https://blog.jcoglan.com/2020/07/31/missing-tls-verification-in-faye/
• https://github.com/faye/faye-websocket-ruby/security/advisories/GHSA-2v5c-755p-p4gv

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