CVE-2020-15824 in Communications Cloud Native Core Policy
Summary
by MITRE
In JetBrains Kotlin from 1.4-M1 to 1.4-RC (as Kotlin 1.3.7x is not affected by the issue. Fixed version is 1.4.0) there is a script-cache privilege escalation vulnerability due to kotlin-main-kts cached scripts in the system temp directory, which is shared by all users by default.
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Analysis
by VulDB Data Team • 01/21/2022
This vulnerability exists in JetBrains Kotlin versions 1.4-M1 through 1.4-RC where the kotlin-main-kts script caching mechanism creates temporary files in the system temp directory that are accessible to all users by default. The flaw stems from insufficient access controls on cached script files that are generated during the execution of kotlin-main-kts scripts, which are designed to execute Kotlin scripts with main functions. When these scripts are processed, they create cached representations in the temp directory that remain accessible to any user on the system, creating a privilege escalation vector. The vulnerability is particularly concerning because it allows any local user to potentially access or modify cached script files created by other users, potentially leading to code execution or information disclosure. The affected versions include the milestone and release candidate builds of Kotlin 1.4 while the 1.3.7x series remains unaffected by this specific issue. This vulnerability directly relates to CWE-276 which addresses improper privilege management and CWE-732 which covers inadequate permissions on critical resources. The operational impact of this vulnerability extends beyond simple privilege escalation as it can enable attackers to execute arbitrary code with elevated privileges or access sensitive information that was previously isolated to specific user contexts. The attack surface is broad since the system temp directory is typically shared and accessible to all users, making this a persistent threat in multi-user environments. The fix implemented in version 1.4.0 addresses the core issue by modifying the caching mechanism to use proper access controls and user-specific temporary directories instead of relying on the shared system temp directory.
The technical implementation of this vulnerability leverages the default behavior of the kotlin-main-kts execution environment which does not enforce strict isolation between user contexts when creating cached script representations. When a Kotlin script is executed through this mechanism, the system generates cached bytecode or intermediate representations that are stored in the system temp directory without proper user-specific access controls. This design flaw creates a scenario where malicious users can potentially read cached files created by other users, or in more sophisticated attacks, can manipulate these cached files to inject malicious code that will execute with the privileges of the original script owner. The vulnerability is particularly dangerous in enterprise environments where multiple users share the same system and where developers may execute scripts with elevated privileges or access to sensitive data. The exploitation of this vulnerability can result in information disclosure, privilege escalation, and potential persistence mechanisms within the affected system. The implementation of proper access controls in version 1.4.0 resolves this by ensuring that cached script files are created in user-specific temporary directories with appropriate permissions that prevent unauthorized access. This remediation aligns with security best practices outlined in the ATT&CK framework under privilege escalation techniques, specifically addressing the use of insecure temporary files and improper access control mechanisms. The vulnerability demonstrates a classic example of how shared system resources can become attack vectors when proper isolation mechanisms are not implemented, and it highlights the importance of considering user context and privilege boundaries in software design.
Organizations affected by this vulnerability should implement immediate mitigation strategies including updating to Kotlin version 1.4.0 or later, which contains the necessary security patches. Additionally, system administrators should review and harden the permissions on system temp directories to ensure that cached files are not accessible to unauthorized users. The vulnerability also underscores the need for comprehensive security testing of scripting environments and temporary file handling mechanisms in development tools. Regular security assessments should include evaluation of how applications handle temporary files and cache storage to prevent similar privilege escalation scenarios. The security implications extend beyond the immediate vulnerability to include potential long-term impacts on system integrity and user data protection. This vulnerability serves as a reminder of the critical importance of proper access control implementation in shared system resources and the need for security-conscious development practices in tooling environments. Organizations should also consider implementing monitoring solutions to detect unusual access patterns to temporary directories that could indicate exploitation attempts. The fix implemented in the patched version demonstrates the importance of addressing security concerns in development tools, as these environments often have elevated privileges and access to sensitive system resources that make them attractive targets for attackers seeking to escalate privileges within a system.