CVE-2026-123831 in CLion
Summary
by MITRE • 11/06/2026
In JetBrains CLion before 2026.2, 2026.1.4 code execution was possible in Safe Mode via Meson project settings
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Analysis
by VulDB Data Team • 11/06/2026
The vulnerability identified in JetBrains CLion versions prior to the release of version 2026.2 represents a critical security flaw within the integrated development environment's handling of build system configurations, specifically targeting projects utilizing the Meson build framework. This issue manifests when users operate under Safe Mode, a configuration intended to restrict potentially harmful operations and enhance stability by disabling certain plugins or features that might interfere with core functionality. Despite these restrictions, attackers who have gained access to the local file system or can influence project settings files are able to execute arbitrary code on the host machine through maliciously crafted Meson build scripts embedded within the project configuration.
The technical root cause of this vulnerability lies in how CLion parses and processes external tool configurations associated with the Meson build system. When a user opens a project configured for Meson, the IDE reads various settings files to determine how to invoke the compiler, linker, and other build tools. In vulnerable versions, the input validation mechanisms applied to these configuration parameters are insufficiently rigorous. Specifically, the application fails to properly sanitize or restrict command-line arguments passed from the project settings to the underlying shell execution context. This lack of strict parameterization allows an attacker who controls the content of a Meson.build file or related configuration artifacts to inject shell metacharacters and arbitrary commands that bypass Safe Mode restrictions.
From an operational perspective, this vulnerability poses significant risks in collaborative development environments where source code is shared via version control systems or received from untrusted third parties. If a developer clones a repository containing a maliciously configured Meson project and opens it in CLion, the IDE may inadvertently execute the embedded commands upon attempting to sync projects or build the solution. This execution occurs with the privileges of the currently logged-in user account, potentially leading to full system compromise if that account possesses administrative rights. The impact extends beyond simple code execution; it can facilitate data exfiltration, installation of persistent backdoors, lateral movement within a network, and disruption of development workflows through resource exhaustion or file corruption.
This flaw aligns with Common Weakness Enumeration category CWE-78 Improper Neutralization of Special Elements used in an OS Command, commonly known as OS Command Injection. The attack vector is classified under MITRE ATT&CK technique T1059 Command and Scripting Interpreter, specifically leveraging shell commands to achieve remote code execution or local privilege escalation depending on the context. Furthermore, because it involves manipulating build system configurations, it relates to CWE-436 Interpretation Conflict, where different components of the software interpret input data in conflicting ways due to inadequate normalization or validation processes.
Mitigation strategies primarily involve upgrading JetBrains CLion to version 2026.2 or later, which addresses these parsing vulnerabilities by implementing stricter sanitization routines for build system parameters and enhancing Safe Mode protections against external tool configuration exploits. In environments where immediate patching is not feasible, developers should exercise extreme caution when opening projects from untrusted sources, even in Safe Mode. It is advisable to manually inspect Meson.build files and other configuration scripts before loading them into the IDE, looking for unusual command invocations or shell escapes. Additionally, organizations should enforce least-privilege principles by ensuring that development accounts do not possess administrative privileges on their host machines, thereby limiting the potential impact of any successful code execution exploit. Regular security audits of build configurations and automated static analysis tools can also help detect such injection points before they are introduced into production repositories.