CVE-2024-23899 is a vulnerability identified in the Jenkins Git server Plugin, specifically in versions 99.va_0826a_b_cdfa_d and earlier. The issue arises from a feature in the plugin's command parser that processes arguments containing an '@' character followed by a file path by replacing this pattern with the contents of the referenced file. This feature, intended for legitimate use cases, is not properly disabled or restricted, allowing attackers who have Overall or Read permissions on the Jenkins instance to exploit this behavior. By crafting arguments that include '@' followed by arbitrary file paths, an attacker can read sensitive files from the Jenkins controller's file system. This vulnerability is classified under CWE-22 (Improper Limitation of a Pathname to a Restricted Directory), indicating a directory traversal or file path manipulation flaw. The vulnerability has a CVSS v3.1 base score of 6.5, reflecting a medium severity level. The attack vector is network-based (AV:N), requires low attack complexity (AC:L), but does require privileges (PR:L) and no user interaction (UI:N). The impact is primarily on confidentiality (C:H), with no impact on integrity or availability. No known exploits are currently reported in the wild, and no patches have been linked yet. This vulnerability allows unauthorized reading of arbitrary files, potentially exposing sensitive configuration files, credentials, or other critical data stored on the Jenkins controller, which could facilitate further attacks or data breaches.

For European organizations, this vulnerability poses a significant risk, especially for those heavily reliant on Jenkins for continuous integration and deployment pipelines. Exposure of sensitive files could lead to leakage of credentials, private keys, or proprietary source code, undermining confidentiality and potentially enabling lateral movement or privilege escalation within the network. Given the widespread adoption of Jenkins in software development across Europe, organizations in sectors such as finance, healthcare, telecommunications, and government could face increased risk. The breach of sensitive data could also lead to compliance violations under GDPR, resulting in legal and financial repercussions. Furthermore, the ability to read arbitrary files without full administrative privileges lowers the barrier for insider threats or compromised accounts to escalate their access to sensitive information. Although the vulnerability does not directly affect system integrity or availability, the confidentiality breach alone can have cascading effects on organizational security posture and trust.

To mitigate this vulnerability, European organizations should first verify the version of the Jenkins Git server Plugin in use and upgrade to a patched version once available from the Jenkins Project. Until a patch is released, administrators should restrict Jenkins user permissions to the minimum necessary, avoiding granting Overall or Read permissions broadly. Implement strict access controls and audit logs to monitor for suspicious usage patterns involving the '@' character in plugin commands. Network segmentation should be employed to limit access to Jenkins controllers to trusted users and systems only. Additionally, organizations can implement Web Application Firewalls (WAFs) or Intrusion Detection Systems (IDS) with custom rules to detect and block attempts to exploit this file reading behavior. Regularly scanning Jenkins instances for configuration weaknesses and applying security best practices, such as disabling unused plugins and enforcing strong authentication mechanisms (e.g., MFA), will further reduce risk. Finally, organizations should prepare incident response plans to quickly address any potential data exposure resulting from exploitation of this vulnerability.