CVE-2020-15134

What it is

Faye before version 1.4.0, there is a lack of certification validation in TLS handshakes. Faye uses em-http-request and faye-websocket in the Ruby version of its client. Those libraries both use 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 `https:` or `wss:` connection made using these libraries is vulnerable to a man-in-the-middle attack, since it does not confirm the identity of the server it is connected to. The first request a Faye client makes is always sent via normal HTTP, but later messages may be sent via WebSocket. Therefore it is vulnerable to the same problem that these underlying libraries are, and we needed both libraries to support TLS verification before Faye could claim to do the same. Your client would still be insecure if its initial HTTPS request was verified, but later WebSocket connections were not. This is fixed in Faye v1.4.0, which enables verification by default. For further background information on this issue, please see the referenced GitHub Advisory.

At a glance

Exploitability

Can be exploited over the network without logging in, but needs a user to act. High risk of data exposure, data tampering.

Exploit odds

0.9% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2020-07-31 18:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 02:56 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.9% in the next 30 days (EPSS).
• Severity: 8.0 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2020-07-31 18:15 UTC

Last modified

2026-06-17 02:56 UTC

Exploit probability

0.9% · EPSS, next 30 days

Weakness

CWE-295 · Improper certificate validation

Record status

Modified

Affected

• Faye Project Faye < 1.4.0

Attack profile CVSS 3.1 · 8.0

Attack vector

Network

Complexity

High

Privileges needed

None

User interaction

Required

Scope

Changed

Confidentiality

High

Integrity

High

Availability

None

Is it in your code?

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