http4k is a functional toolkit for Kotlin HTTP applications, designed to provide a simple, consistent and flexible way to build web services and applications. It is widely used by developers for its concise, testable and modular nature. However, prior to version 5.41.., there is a potential XXE (XML External Entity Injection) vulnerability present when http4k handles malicious XML contents within requests.
This vulnerability could allow attackers to exploit the server by reading local sensitive information, triggering Server-side Request Forgery (SSRF), and potentially executing code under specific circumstances.
Description of Vulnerability
The issue at hand involves XXE injections, where an attacker can exploit the XML parsing functionality of http4k by sending malicious XML contents in a request to a server that uses http4k. This can lead to attacks such as reading sensitive information from the server, triggering SSRF, and in specific environments, executing malicious code.
A classic example of an XXE injection payload looks something like this
<?xml version="1." encoding="ISO-8859-1"?>
<!DOCTYPE foo [
<!ELEMENT foo ANY >
<!ENTITY xxe SYSTEM "file:///etc/passwd" >]>
<foo>&xxe;</foo>
In this example, the attacker is trying to include the contents of /etc/passwd via an external entity. Once an http4k-based server processes this request, the contents of /etc/passwd would be exposed to the attacker, hence leaking sensitive information.
Original References
The vulnerability was first reported in this GitHub issue (replace XYZ with the actual issue number), where the http4k maintainers acknowledged the issue and later released a patch for it in version 5.41.., which can be found in this GitHub commit (replace abc123 with the actual commit hash).
The patch is also mentioned in the http4k CHANGELOG under the corresponding version.
Exploitation Details
To exploit this vulnerability, an attacker would have to craft a malicious XML payload and send it as a request to a server running an http4k version prior to 5.41... The server, in turn, would process the payload, leading to XML External Entity Injection. The severity of the exploitation depends on the environment and permissions of the server.
Mitigation and Recommendations
The http4k maintainers have released a patch for this vulnerability in version 5.41... It is highly recommended to update your http4k dependency to at least version 5.41.. to eliminate the risk of this vulnerability.
Update your dependency by changing the version in your build file. For example, if you're using Gradle, update your build.gradle file:
dependencies {
implementation 'org.http4k:http4k-core:5.41..'
}
In addition to updating the http4k library, it is essential to maintain good security practices, such as:
Regularly reviewing the security of your code and dependencies.
3. Following the Principle of Least Privilege (POLP) when granting permissions to your server and applications.
Timeline
Published on: 12/12/2024 19:15:13 UTC
Last modified on: 12/13/2024 15:15:42 UTC