The CVE-2022-39348 refers to a Cross-Site Scripting (XSS) vulnerability discovered in the twisted.web.vhost.NameVirtualHost implementation provided by the Twisted framework. The issue results in the possible injection of HTML and script content through the Host header in the 404 response payload when the header does not match any of the configured hosts. This vulnerability affects versions of Twisted starting from .9.4 and was patched in version 22.10.rc1.

In most scenarios, this vulnerability can be challenging to exploit, as modifying the Host header implies the attacker has already gained a privileged position within the network. However, it is still important to be aware of this vulnerability and make sure you are using the patched version of the library to avoid potential risks.


The main impact of this vulnerability is that an attacker can inject malicious HTML and script content into the 404 response payload when the Host header does not match any of the configured hosts. This can lead to unwanted changes to the display of the affected web application and can provide the attacker with an opportunity for further attacks, such as stealing user information or executing arbitrary code in the victim's browser.

Below is an example of how the vulnerability can be triggered

from twisted.web import vhost
from twisted.web import server
from twisted.internet import reactor

resource = vhost.NameVirtualHost()
site = server.Site(resource)

reactor.listenTCP(808, site)

In this example, a NameVirtualHost object is created, and any incoming request with a non-matching Host header will cause the NoResource object to be returned with unescaped Host header injected in the 404 response:

HTTP/1. 404 Not Found
Content-Length: 141
Content-Type: text/html
Server: TwistedWeb/17.9.
Date: Wed, 18 Oct 2022 18:26:52 GMT

<!DOCTYPE html>
<title>404 - No Such Resource</title>
<pre>no such child resource: &lt;script&gt;alert('xss')&lt;/script&gt;</pre>


- Twisted Framework Release Notes:
- CVE-2022-39348 Vulnerability Details:
- Twisted Documentation:

Exploit Details

Currently, there are no publicly known exploits for this specific vulnerability. However, attackers could potentially use other more common techniques, such as injecting malicious scripts in compromised web applications, to modify the Host header and trigger the vulnerability.


There are no known workarounds for this vulnerability. It is highly recommended to update the Twisted framework to the patched version (22.10.rc1) to avoid any potential risks.


Although the CVE-2022-39348 vulnerability appears to be difficult to exploit in practice, it is still crucial to update the Twisted framework to the latest version to ensure the safety and security of your web applications. By keeping your software up-to-date, you reduce the attack surface for potential attackers and minimize the risk of falling victim to security issues like this one.


Published on: 10/26/2022 20:15:00 UTC
Last modified on: 03/08/2023 01:07:00 UTC