Improper Certificate Validation in Faye

1) Improper Certificate Validation

EUVDB-ID: #VU45885

Risk: High

CVSSv3.1: 7.6 [CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2020-15134

CWE-ID: CWE-295 - Improper Certificate Validation

Exploit availability: No

Description

The vulnerability allows a remote non-authenticated attacker to read and manipulate data.

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.

Mitigation

Install update from vendor's website.

Vulnerable software versions

Faye: 1.0.0 - 1.3.0

External links

http://blog.jcoglan.com/2020/07/31/missing-tls-verification-in-faye/
http://github.com/faye/faye/security/advisories/GHSA-3q49-h8f9-9fr9

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.