CVE-2026-104126 in JumpServer
Summary
by MITRE • 10/13/2026
JumpServer is an open source bastion host and an operation and maintenance security audit system. Prior to 4.10.17-lts, JumpServer's Ansible-based automation rendering can evaluate attacker-controlled template expressions from users who have permission to create or execute affected automation tasks. Crafted content can invoke sensitive Ansible lookup behavior, including file, pipe, env, and password lookups, within the Ansible execution context, which can disclose files or environment values and may permit limited command execution under the privileges of the automation process. The issue does not provide unauthenticated access or direct access to unrelated JumpServer assets. This issue is fixed in version 4.10.17-lts.
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Analysis
by VulDB Data Team • 10/13/2026
JumpServer serves as a critical component in modern infrastructure security, functioning as an open-source bastion host and operation and maintenance security audit system that centralizes access control for administrative activities. Within this ecosystem, the platform incorporates Ansible-based automation rendering to facilitate complex operational tasks through templated configurations. However, versions prior to 4.10.17-lts contain a significant vulnerability where the template engine fails to adequately sanitize inputs from users who possess permissions to create or execute automated tasks. This architectural flaw allows attackers with such privileges to inject crafted content that is interpreted as executable code rather than static data during the rendering process, effectively bypassing intended security boundaries within the automation workflow.
The technical core of this vulnerability lies in the evaluation of attacker-controlled template expressions by the Ansible engine. When a user submits an automated task definition containing maliciously constructed templates, the system processes these inputs without sufficient validation against dangerous lookup functions. Specifically, the flaw enables the invocation of sensitive Ansible lookups such as file, pipe, env, and password retrievals within the context of the automation process. This capability transforms what should be a controlled configuration mechanism into an arbitrary code execution vector, allowing the attacker to read restricted files from the underlying operating system or extract environment variables that may contain secrets, API keys, or other sensitive credentials stored in plain text or accessible formats.
The operational impact of this vulnerability is substantial for organizations relying on JumpServer for privileged access management and automated maintenance. An authenticated user with task creation privileges can leverage these lookup functions to exfiltrate data from the server hosting the automation engine, potentially leading to further compromise of adjacent systems if sensitive credentials are discovered. While the vulnerability does not grant unauthenticated remote code execution or direct lateral movement to unrelated JumpServer assets, it represents a severe breach of trust within the administrative boundary. The ability to execute commands under the privileges of the automation process means that an attacker could escalate their influence beyond mere data disclosure, potentially disrupting services or installing persistent backdoors depending on the permissions assigned to the Ansible execution user account.
From a classification perspective, this vulnerability aligns with CWE-94 Improper Control of Generation of Code (Code Injection) and specifically relates to template injection flaws where untrusted input is used in dynamic code generation without proper sanitization. In terms of adversary behavior, it maps to ATT&CK techniques involving Command and Scripting Interpreter abuse for lateral movement or credential access, as well as Data from Local System Retrieval through the exploitation of lookup plugins that interact with the host environment. The attack vector requires initial authentication and specific role-based permissions, indicating a need for strict adherence to least privilege principles within JumpServer’s RBAC model.
To mitigate this risk, organizations must immediately upgrade their JumpServer instances to version 4.10.17-lts or later, where the template rendering engine has been hardened against such injection attacks. In addition to patching, administrators should review and restrict user permissions related to automation task creation, ensuring that only highly trusted personnel can define complex Ansible playbooks. Implementing strict input validation at the application layer for any fields passed to templating engines is also recommended as a defense-in-depth measure. Regular audits of automated tasks and monitoring for unusual patterns in template usage can help detect potential exploitation attempts before they result in significant data loss or system compromise.