A new security vulnerability has been identified in Jenkins, an open-source automation server that facilitates the automation of various continuous integration workflows. The vulnerability, tracked as CVE-2023-43497, affects Jenkins' Stapler web framework while processing file uploads. Specifically, the issue occurs in Jenkins 2.423 and earlier, as well as LTS 2.414.1 and earlier versions.

In this post, we will dive deeper into the details of this vulnerability, provide code snippets to demonstrate the issue, and offer links to original references. Ultimately, understanding the impact and actual exploit of this vulnerability will help users in securing their Jenkins installations better.

Vulnerability Details

The vulnerability arises when Jenkins processes file uploads using the Stapler web framework. During this process, the uploads temporarily create files in the default system temporary directory with the default permissions for new files.

Consequently, this may potentially allow attackers with access to the Jenkins controller file system to read and write the files before they are used. In other words, unauthorized users can potentially exploit this vulnerability to gain access to sensitive information or tamper with the existing data in Jenkins' temporary files.

Here's a code snippet that demonstrates the vulnerability in the Stapler framework

import jenkins.stapler.FileItem;
import java.io.File;

public class FileUploadHandler {

    public HttpResponse doUploadFile(FileItem file) {
        File tempDir = new File(System.getProperty("java.io.tmpdir"));
        File tempFile = new File(tempDir, file.getName());
        // Process the uploaded file

        return HttpResponses.redirectTo("uploadsuccess");

In this code example, the doUploadFile method handles file uploading by creating a new temporary file in the default system temporary directory (tempDir). The temporary file is created with default file permissions, which might provide unauthorized access to attackers.


To exploit this vulnerability, an attacker would need access to the Jenkins controller file system. After gaining access, an attacker can monitor the temporary directory for any new files created during the file upload process, providing them with an opportunity to read or tamper with sensitive data.

Moreover, the attacker could potentially use a race condition or timing attack to gain unauthorized access to these temporary files, thereby compromising the integrity of the Jenkins environment.

Mitigation and Resolution

Jenkins users are encouraged to upgrade their installations to the latest versions, as the issue has been resolved in Jenkins 2.424 and LTS 2.414.2. Upgrading to these versions will ensure that temporary files are created with restricted permissions, preventing unauthorized access to the files.

Furthermore, it is essential to follow best practices for securing your Jenkins installation, such as keeping your environment up-to-date, implementing proper access controls, and ensuring that your network and system configurations follow security best practices.

For more information on this vulnerability, please refer to the following resources

1. Jenkins Security Advisory: https://www.jenkins.io/security/advisory/2023-10-14/
2. CVE-2023-43497 Details: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-43497


CVE-2023-43497 poses a significant security risk for Jenkins users running affected versions, as it allows unauthorized access to temporary files during the file upload process. Understanding the exploit details and implementing necessary security measures, such as upgrading your Jenkins installation and following security best practices, will help protect your environment from potential attacks.


Published on: 09/20/2023 17:15:11 UTC
Last modified on: 09/23/2023 03:45:05 UTC