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CVE-2024-23897 is a critical security vulnerability discovered in the Jenkins automation server command-line interface.
The flaw specifically affects how command-line arguments are parsed and processed by the underlying args4j library.
Jenkins enables a feature called expandAtFiles by default within its CLI protocol handling mechanisms.
When an incoming command argument contains an at sign character followed by a file path, the parser intercepts it.
Instead of treating the input as a literal string, the parser reads the external file from disk.
It then replaces the argument value entirely with the complete contents of the targeted system file.
This design flaw lacks sufficient permission checks and path sanitization constraints for unauthenticated or low-privilege sessions.
Remote actors can exploit this behavior over HTTP, WebSocket, or SSH protocols without requiring valid authentication tokens.
By passing crafted inputs containing file paths, attackers can extract sensitive configuration data and credentials.
The extent of file disclosure depends on the caller’s permissions and the specific CLI commands available.
On Windows operating systems, legacy character encoding practices further facilitate reading binary application files and master keys.
Exposed cryptographic keys or session secrets can subsequently be leveraged to forge administrative cookies or execute remote code.
The vulnerability received a maximum CVSS base score of 9.8 due to its severe impact on system confidentiality and integrity.
CISA added this flaw to its Known Exploited Vulnerabilities catalog following active exploitation campaigns in the wild.
Organizations utilizing unpatched build servers faced massive exposure across internal and external network perimeters.
Mitigating this issue requires upgrading core server instances and ensuring secure plugin and CLI configurations.
DailyCVE Form:
Platform: Jenkins Automation Server
Version: Versions 2.441 earlier
Vulnerability: Arbitrary File Read
Severity: Critical security score
date: January 24 2024
Prediction: Patched January 2024
What Undercode Say:
Bash commands and code snippets demonstrating interaction with the Jenkins CLI endpoint and configuration validation:
python3 jenkins_fileread.py --url http://jenkins.local:8080 --file /etc/passwd
pipeline {
agent any
stages {
stage('Preflight Check') {
steps {
sh 'java -version'
sh 'syft version'
}
}
}
}
Exploit: (Educational Purposes!)
The exploit leverages the unauthenticated HTTP CLI endpoint where argument expansion is active. By issuing a request with an argument structured as @/path/to/target, the args4j parser reads the file and returns its data in the error message or command response stream. Attackers target sensitive configuration files, logs, and private keys to escalate privileges.
Protection: from this CVE
Upgrade Jenkins core to version 2.442 or later (or supported LTS releases) where argument expansion is disabled by default. Administrators can also mitigate the risk by completely disabling CLI access or setting the Java system property to restrict command-line parsing behavior. Ensure all plugins and CLI tools are updated to secure versions.
Impact:
Successful exploitation allows unauthenticated attackers to read sensitive files from the controller file system. This leads to information disclosure, credential theft, session hijacking, and ultimate compromise of the entire CI/CD infrastructure through remote code execution.
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Sources:
Reported By: github.com
Extra Source Hub:
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