In this post, we will discuss the details of a security vulnerability identified by the CVE number 2023-40167. The vulnerability is related to Jetty, a widely-used Java-based web server and servlet engine that does not properly validate the content-length value in HTTP/1 header fields. We will cover how this issue can potentially lead to request smuggling attacks, the affected Jetty versions, and how users can patch their server to resolve this security risk.

As mentioned, Jetty is a popular Java web server and servlet engine designed for serving up HTTP content. According to the information provided by the respective CVE (CVE-2023-40167), Jetty versions 9.4.52, 10..16, 11..16, and 12..1 contain a patch for an issue wherein the application accepts the + character before the content-length value in a HTTP/1 header field.

This behavior is not compliant with the RFC standards and other web servers usually reject such requests with 400 response codes. Although there is no known exploit scenario at this time, it is possible that request smuggling could result if Jetty is used in combination with a server that does not close the connection after sending such a 400 response.

Request smuggling is a type of attack that can potentially lead to unauthorized access to protected resources or cause other undesirable outcomes on the targeted server. This occurs when an attacker manipulates HTTP requests in a way that confuses the server, causing it to interpret them incorrectly and potentially allowing the attacker to execute malicious actions on the affected system.

In the case of CVE-2023-40167, Jetty allowing the + character before the content-length value in a HTTP/1 header field could lead to a request smuggling scenario if a secondary server does not terminate the connection as expected after sending a 400 response. To better understand the issue, let us take a look at an example of a problematic HTTP/1 header field:

Content-Length: +5

According to the RFC, the + character should not be allowed before the content-length value. However, Jetty versions affected by this vulnerability will accept and process these requests.

To fix this issue, Jetty has released patches (available in versions 9.4.52, 10..16, 11..16, and 12..1) which properly validate the content-length value to be compliant with the RFC standards. Users are encouraged to update their Jetty installations to these patched versions to mitigate this vulnerability.

There is no workaround available for this issue, as there is no known exploit scenario. For more information and to keep up-to-date on this security vulnerability, consult the official references:

- CVE-2023-40167 Details
- Jetty Project Home Page
- Jetty Security Advisory

In conclusion, it's essential to keep your Jetty web server up-to-date to ensure that potential vulnerabilities, such as CVE-2023-40167, are addressed. Staying vigilant about security patches and regularly reviewing the best practices for server configuration will provide a more robust defense against possible attack scenarios.

Timeline

Published on: 09/15/2023 20:15:09 UTC
Last modified on: 10/13/2023 01:59:32 UTC