CVE-2026-84671 in File Parameter Plugin
Summary
by MITRE • 09/02/2026
Jenkins File Parameter Plugin 425.v3fa_801681b_5e and earlier allows writing files to arbitrary locations on the Jenkins controller file system through Stapler data binding, which can lead to remote code execution.
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Analysis
by VulDB Data Team • 09/02/2026
The vulnerability identified in Jenkins File Parameter Plugin versions prior to 425.v3fa_801681b_5e represents a critical security flaw rooted in improper validation of user-supplied input during file system operations. This issue specifically affects the Stapler data binding mechanism, which is responsible for mapping HTTP request parameters to Java object properties within the Jenkins controller environment. When users submit pipeline configurations or form inputs that include file path specifications, the plugin fails to adequately sanitize these paths before processing them. Consequently, an attacker can manipulate the input to traverse directory boundaries and specify arbitrary locations on the underlying operating system's file structure rather than restricting writes to intended temporary directories.
This lack of strict path validation allows for a classic Path Traversal attack vector, technically classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory. By exploiting this flaw, an authenticated attacker with access to the Jenkins interface can write files to sensitive system locations such as /etc/passwd on Linux systems or critical configuration directories within the Windows registry structure. The ability to overwrite arbitrary files is particularly dangerous because it bypasses standard application-level permissions and interacts directly with the operating system's file integrity controls. This capability undermines the fundamental security boundary between the web application layer and the host infrastructure, effectively granting the attacker write access equivalent to that of the user account running the Jenkins controller process.
The operational impact of this vulnerability extends far beyond simple data corruption or unauthorized information disclosure. Because Jenkins controllers typically run with elevated privileges to manage build agents and execute complex CI/CD pipelines, writing malicious scripts or configuration files to specific locations can lead directly to Remote Code Execution. For instance, an attacker could overwrite a script that is automatically executed during the next pipeline run, inject code into startup configurations, or replace legitimate library files used by Jenkins plugins. This transforms the vulnerability from a local file manipulation issue into a full system compromise scenario where the attacker gains persistent control over the CI/CD infrastructure. Such access allows for further lateral movement within the network, theft of sensitive credentials stored in Jenkins secrets management systems, and disruption of critical software delivery pipelines.
From an attack perspective, this flaw aligns with MITRE ATT&CK techniques related to Command and Scripting Interpreter abuse as well as File Manipulation tactics used by adversaries to establish persistence or execute arbitrary commands without deploying traditional malware binaries. The exploitation requires authenticated access, which means the threat actor must already have valid credentials for a Jenkins user account capable of triggering file parameter operations. However, given that many organizations use shared service accounts with broad permissions in their CI/CD environments, this prerequisite is often easily met by internal threats or compromised developer workstations.
To mitigate this risk, administrators should immediately upgrade the File Parameter Plugin to version 425.v3fa_801681b_5e or later, where the developers have implemented stricter input validation and path canonicalization checks to prevent directory traversal attacks. In addition to patching, organizations should enforce Principle of Least Privilege by ensuring that Jenkins controller processes run under dedicated service accounts with minimal file system permissions rather than administrative rights. Network segmentation strategies can also help limit the blast radius if an attacker does manage to execute code on the controller node. Regular auditing of plugin versions and continuous monitoring for unusual file system activity around Jenkins directories are recommended practices to maintain a robust security posture against such exploitation attempts.