CVE-2026-31864 in JumpServer
Summary
by MITRE • 03/13/2026
JumpServer is an open source bastion host and an operation and maintenance security audit system. a Server-Side Template Injection (SSTI) vulnerability exists in JumpServer's Applet and VirtualApp upload functionality. This vulnerability can only be exploited by users with administrative privileges (Application Applet Management or Virtual Application Management permissions). Attackers can exploit this vulnerability to execute arbitrary code within the JumpServer Core container. The vulnerability arises from unsafe use of Jinja2 template rendering when processing user-uploaded YAML configuration files. When a user uploads an Applet or VirtualApp ZIP package, the manifest.yml file is rendered through Jinja2 without sandbox restrictions, allowing template injection attacks.
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Analysis
by VulDB Data Team • 03/20/2026
The vulnerability identified as CVE-2026-31864 represents a critical Server-Side Template Injection flaw within JumpServer's application architecture, specifically affecting the Applet and VirtualApp upload functionalities. This security weakness exists within an open-source bastion host and operations security audit system that serves as a central control point for enterprise infrastructure access management. The vulnerability's exploitation requires administrative privileges, specifically targeting users with Application Applet Management or Virtual Application Management permissions, which aligns with privilege escalation attack patterns documented in the MITRE ATT&CK framework under privilege escalation techniques. The affected system operates as a core security infrastructure component that manages access to enterprise resources, making this vulnerability particularly dangerous as it provides attackers with elevated execution capabilities within the JumpServer Core container environment.
The technical root cause of this vulnerability stems from the unsafe implementation of Jinja2 template rendering processes when handling user-uploaded YAML configuration files. During the processing of ZIP packages containing Applet or VirtualApp configurations, the system parses and renders manifest.yml files through Jinja2 templating without implementing proper sandboxing restrictions or input validation mechanisms. This unsafe template processing approach creates an environment where maliciously crafted template code can be executed within the application context, directly exposing the underlying system to arbitrary code execution attacks. The vulnerability manifests as a direct consequence of inadequate template security controls, which corresponds to CWE-74 principles related to improper neutralization of special elements used in template engine commands. The absence of proper template isolation allows attackers to inject template syntax that gets interpreted and executed by the Jinja2 engine, bypassing normal input validation and security boundaries.
The operational impact of this vulnerability extends beyond simple code execution capabilities, as it provides attackers with complete control over the JumpServer Core container environment. This elevated privilege execution allows for comprehensive system compromise including potential lateral movement within the enterprise network, data exfiltration, and further exploitation of other system components. The vulnerability's exploitation path requires administrative access but once achieved, it creates a persistent backdoor within the security infrastructure itself, fundamentally undermining the trust model that JumpServer is designed to enforce. The attack surface is particularly concerning because it targets the core operational security functions of the system, potentially allowing adversaries to evade detection mechanisms while gaining access to sensitive infrastructure resources. Organizations relying on JumpServer for privileged access management face significant risk as this vulnerability could enable attackers to establish long-term access to critical network assets.
Mitigation strategies for this vulnerability should focus on implementing proper template sandboxing and input validation controls within the JumpServer application. The immediate remediation involves configuring Jinja2 template rendering to operate within restricted environments that prevent execution of arbitrary code, implementing strict input validation for uploaded YAML files, and applying proper privilege separation mechanisms. Organizations should also consider implementing additional security controls such as mandatory access controls, network segmentation, and enhanced monitoring of upload activities to detect anomalous behavior. The solution approach should align with the principle of least privilege by ensuring that administrative functions are properly audited and that template processing occurs in isolated environments. Security teams should also implement automated vulnerability scanning processes that can detect similar template injection patterns in other components of the system, following established security frameworks and standards such as those defined by NIST and ISO 27001 for secure application development practices.