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

> The Faye WebSocket library fails to verify TLS certificates, allowing attackers to perform man-in-the-middle attacks on secure connections.

- **Severity:** High 8.0 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 31 Jul 2020
- **Updated:** 4 Aug 2024
- **Also known as:** DEBIAN-CVE-2020-15133, GHSA-2v5c-755p-p4gv, UBUNTU-CVE-2020-15133

## What is CVE-2020-15133?

CVE-2020-15133 is a high-severity vulnerability in faye-websocket, published on 31 Jul 2020. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-295 (Improper Certificate Validation)

## Which versions are affected by CVE-2020-15133?

2 open source packages ship an affected version, including faye-websocket. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `faye-websocket` | RubyGems | All versions | 0.11.0 |
| `faye-websocket` | RubyGems | All versions | 0.11.0 |

Products: Faye-Websocket Project Faye-Websocket.

## How do I fix CVE-2020-15133?

Upgrade faye-websocket to 0.11.0 or later.

## Is CVE-2020-15133 being exploited?

There is no known exploitation of CVE-2020-15133 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-15133 and fix it if it is affected.

What it is: CVE-2020-15133 is a high-severity vulnerability in faye-websocket, published on 31 Jul 2020. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2020-15133 in the wild and no public exploit code.

Affected packages and fixed versions:
- faye-websocket (RubyGems): affected all versions; fixed in 0.11.0
- faye-websocket (RubyGems): affected all versions; fixed in 0.11.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2020-15133/ (Markdown: https://insights.sbomify.com/CVE-2020-15133/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-15133
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-15133
- OSV: https://osv.dev/vulnerability/CVE-2020-15133

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-15133/
Summaries are generated and may contain mistakes; the official description above is the record.