CVE-2018-1000409: Session Fixation in Jenkins
Summary
CVE-2018-1000409: Session Fixation in Jenkins. Affects org.jenkins-ci.main:jenkins-core across 2 version ranges.
< 2.138.2
>= 2.140, < 2.146
Fixed in 2.138.2 or 2.146, depending on the release line you run. How to fix ↓
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Background
Jenkins is an open-source automation server that enables developers to build, test, and deploy their software projects. It is widely used for continuous integration and delivery. The Jenkins core package, specifically the 'jenkins-core' module, is responsible for the fundamental functionality of the Jenkins server. This vulnerability affects versions 2.145 and earlier, as well as LTS 2.138.1 and earlier.
Vulnerability Detail
The vulnerability identified as CVE-2018-1000409 is a session fixation vulnerability in Jenkins. The issue resides in the 'HudsonPrivateSecurityRealm.java' file within the 'jenkins-core' package. Prior to the fix, Jenkins failed to invalidate existing user sessions and create new ones when a user signed up for a new account. This flaw could allow an attacker to fixate a user's session and potentially gain unauthorized access to their account or perform malicious actions on their behalf.
How To Fix
Latest published version: 2.587 as of 22 Oct 2026
Upgrading to it may include breaking changes; the versions below are the minimum fixed release for this vulnerability.
If you can't move to the latest
The minimum fixed version depends on the release line you run.
-
< 2.138.22.138.2 -
>= 2.140, < 2.1462.146
Tip — Not sure which release line you're on? Vulert can find the fix for the version you are using. Scan free →
Workaround
As a temporary workaround, users can manually invalidate their sessions and create new ones by logging out and logging back in after signing up for a new account. This will ensure that the session fixation vulnerability is mitigated. However, it is strongly advised to apply the official fix by updating the 'jenkins-core' package as soon as possible.
Conclusion
In conclusion, the session fixation vulnerability in Jenkins 2.145 and earlier, as well as LTS 2.138.1 and earlier, poses a moderate risk to the security of Jenkins installations. It is recommended to update the 'jenkins-core' package to version 2.138.2 or later to address this vulnerability. Users can also manually invalidate their sessions and create new ones as a temporary workaround. For further assistance or support in vulnerability remediation, please contact DevNack.com.
See every vulnerability recorded for org.jenkins-ci.main:jenkins-core →
FAQ
Jenkins is an open-source automation server used for continuous integration and delivery. It helps developers automate the building, testing, and deployment of their software projects.
The 'jenkins-core' package is a fundamental module of Jenkins that provides core functionality to the Jenkins server. It is responsible for handling user authentication, session management, and other essential features.
Session fixation is a type of attack where an attacker fixes or sets a user's session ID, allowing them to hijack the user's session and potentially gain unauthorized access to their account or perform malicious actions on their behalf.
You can use the Vulert Playground (https://vulert.com/scanner) to check if your Jenkins installation is affected by this vulnerability. Simply provide your 'pom.xml' file, and Vulert will analyze it in real-time and alert you if any open-source vulnerabilities, including this one, are detected.
As of the latest information available, there are no known public exploits for this vulnerability. However, it is crucial to apply the fix promptly to mitigate the risk of potential exploitation.
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