CVE-2019-10400 in Script Security Plugin
Summary
by MITRE
A sandbox bypass vulnerability in Jenkins Script Security Plugin 1.62 and earlier related to the handling of subexpressions in increment and decrement expressions not involving actual assignment allowed attackers to execute arbitrary code in sandboxed scripts.
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Analysis
by VulDB Data Team • 08/22/2020
The vulnerability identified as CVE-2019-10400 represents a critical sandbox bypass flaw within the Jenkins Script Security Plugin affecting versions 1.62 and earlier. This security weakness specifically targets the plugin's handling of subexpressions within increment and decrement operations that do not involve direct assignment. The issue arises from insufficient validation mechanisms that fail to properly isolate potentially dangerous code constructs within the sandboxed execution environment. Attackers can exploit this vulnerability by crafting malicious scripts that leverage the improper handling of these specific expression types to escape the intended security boundaries of the sandbox.
The technical root cause of this vulnerability stems from the plugin's inadequate parsing and validation of increment and decrement expressions that operate on variables without assignment operations. When Jenkins processes these expressions within the script security context, the system fails to properly sanitize or restrict the execution paths that could lead to arbitrary code execution. This flaw allows attackers to manipulate the script execution flow through carefully constructed subexpressions that bypass the normal security checks designed to prevent unauthorized operations. The vulnerability specifically affects the Script Security Plugin's ability to distinguish between safe and dangerous code patterns during the compilation phase of sandboxed scripts.
From an operational perspective, this vulnerability poses significant risks to Jenkins environments since it allows attackers with minimal privileges to execute arbitrary code within the sandboxed context. The impact extends beyond simple privilege escalation as it enables full compromise of the Jenkins server through code execution. Attackers can leverage this vulnerability to gain access to sensitive build configurations, credentials stored within the Jenkins environment, and potentially use the compromised system as a launch point for further attacks within the network infrastructure. The vulnerability's exploitation requires only basic script writing skills and does not demand advanced technical knowledge, making it particularly dangerous in environments where multiple users have script execution privileges.
Security practitioners should implement immediate mitigations including upgrading the Script Security Plugin to version 1.63 or later, which contains the necessary patches to address the sandbox bypass vulnerability. Organizations should also review their Jenkins configurations to ensure that only trusted administrators have the ability to create or modify scripts, and consider implementing additional monitoring for unusual script execution patterns. The vulnerability aligns with CWE-252, which describes an insufficient validation of the security of a system, and maps to ATT&CK technique T1059.007 for execution through scripting, specifically targeting the sandbox escape capabilities that allow attackers to bypass security controls. Regular security assessments and patch management processes should be strengthened to prevent similar vulnerabilities from remaining unaddressed in critical infrastructure components.