Note: If jul893 refers to a specific internal ticket, a unique repository vulnerability, or a lesser-known CVE, the technical details below regarding the Jenkins Arbitrary File Read are the industry standard for this type of recent "patched" critical alert. If you meant a different vulnerability, please provide the product name. Here is the full write-up for the critical vulnerability commonly tracked in this context.
Vulnerability Write-Up: Jenkins CLI Arbitrary File Read (CVE-2024-23897) Executive Summary In January 2024, a critical security vulnerability was patched in the Jenkins continuous integration server. The vulnerability allows unauthenticated attackers to read arbitrary files on the Jenkins controller file system. Given that Jenkins often stores secrets, credentials, and private keys, this vulnerability poses a severe supply chain security risk.
Vulnerability: Arbitrary File Read CVE ID: CVE-2024-23897 CVSS Score: 9.8 (Critical) Affected Versions: Jenkins Weekly <= 2.441, Jenkins LTS <= 2.426.2 Patch Status: Patched in Weekly 2.442 and LTS 2.426.3
Technical Details The Root Cause The vulnerability resides in the Jenkins CLI (Command Line Interface) argument parser. Jenkins uses the args4j library to parse command arguments. The flaw exploits how the CLI handles the @ character followed by a file path. In args4j , this syntax is a standard feature intended to load arguments from a file (similar to shell expansion). The mechanism: jul893 patched
An attacker connects to the Jenkins CLI port (typically 50000/tcp or via HTTP/HTTPS). The attacker sends a command (like help or who-am-i ) with an argument starting with @ , e.g., @/etc/passwd . The args4j library attempts to resolve this path. Instead of treating it as a literal string argument, it reads the file located at that path and uses its contents as the argument for the command. When the command fails or returns help text, Jenkins often includes the "invalid" arguments (the file content) in the error message or stdout sent back to the attacker.
Attack Vector While the vulnerability is exploited via the CLI, it does not require valid CLI credentials if the Jenkins instance allows anonymous read access (which is a common default configuration for the CLI). Even if authentication is required, the file read occurs before the CLI command is fully executed in some contexts, or the error messages leak enough data to compromise the system.
Proof of Concept (PoC) An attacker can use the standard java -jar jenkins-cli.jar or a custom socket script to exploit this. Scenario: Reading /etc/passwd from the server. Command: java -jar jenkins-cli.jar -s http://target-jenkins/ -webSocket help "@/etc/passwd" Note: If jul893 refers to a specific internal
Outcome: If vulnerable, the Jenkins controller reads /etc/passwd and attempts to use the content of that file as arguments for the help command. The error message or output returned to the attacker will contain the contents of /etc/passwd . Impact Expansion: Attackers can pivot from reading system files to reading Jenkins-specific files:
/var/jenkins_home/secrets/master.key : Used to decrypt stored credentials. /var/jenkins_home/secrets/hudson.util.Secret : The encryption key itself. /proc/self/environ : To steal environment variables (often containing cloud API keys).
Once the master.key and hudson.util.Secret are exfiltrated, an attacker can decrypt all credentials stored in Jenkins (SSH keys, AWS secrets, Git tokens) offline. Hardening: Even if a command fails
The Patch The Jenkins security team addressed this by disabling the argument file expansion feature by default in the CLI argument parser. Changes made:
Update to args4j handling: The patch modifies how the CLI parses arguments, explicitly rejecting or sanitizing arguments that begin with the @ symbol. Hardening: Even if a command fails, the output is sanitized to prevent file contents from being reflected back to the user in error messages.