External risk intelligence

JetBrains CLion Safe Mode JSON Code Execution Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.6)

CVE-2026-123832

JetBrains CLion is a desktop-based Integrated Development Environment (IDE) used primarily by individual developers locally. It is not an internet-facing service, edge gateway, or public-facing application, and its deployment is confined to the user's local workstation environment.

Halo Surface Signal: 1 out of 5 — much less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A vulnerability has been identified in JetBrains CLion, potentially allowing code execution when using Safe Mode through a JSON compilation database. This issue is categorized as critical, indicating a high potential for impact. The main concern is to confirm whether our environment utilizes this specific software and is potentially exposed.

Code execution possible in Safe Mode.
Confirm relevance for affected software.
Understand potential, if applicable.

Attack Path

How an attacker could exploit the issue

An attacker could trick a user into opening a specially crafted JSON compilation database file within JetBrains CLion. This could lead to the attacker executing arbitrary code on the user's machine, potentially impacting confidentiality, integrity, and availability.

No authentication or user interaction needed.
Opening a malicious JSON compilation database.
Arbitrary code execution.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could allow an attacker to execute arbitrary code on a user's system when they open a specially crafted JSON compilation database file in JetBrains CLion in Safe Mode. This could potentially lead to a compromise of the user's local development environment.

User's local development environment.
Opening a malicious JSON file.
Arbitrary code execution on the workstation.

Operational Fix

Recommended remediation, mitigation, and detection steps

JetBrains CLion, a desktop IDE, is primarily used by individual developers on their local machines. The first step is to identify all workstations running CLion, confirm if the affected version is in use, and then engage individual developers or development team leads to address the vulnerability.

Development teams/individual developers.
Confirm CLion usage and version.
Coordinate updates with developers.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is JetBrains CLion?

JetBrains CLion is an integrated development environment, or IDE, specifically designed for C and C++ programming. Developers use it to write, debug, and manage complex software projects. It acts as a comprehensive workspace that simplifies compiling and building applications across various platforms.

What does CWE-829 mean for CVE-2026-123832?

CWE-829 refers to the inclusion of functionality from an untrusted control sphere. In the context of this CVE, it means the software fails to properly validate external files, allowing a malicious JSON compilation database to trick the application into executing code that the developer did not authorize or intend.

How does an attacker trigger this vulnerability?

An attacker must convince a user to open a specially crafted, malicious JSON compilation database file within CLion while it is in Safe Mode. The vulnerability does not trigger through normal, everyday usage of the IDE; it requires this specific file interaction to bypass security controls.

Is my computer at risk according to Halo Surface Signal?

According to Halo Surface Signal, this is very unlikely. CLion is a desktop-based application used locally on individual workstations rather than a public-facing network service or internet gateway. Because it does not run as a server exposed to the public internet, the attack surface is significantly limited to physical or local workstation access.

How should I respond if I use CLion?

First, verify which version of CLion is currently installed on your workstation to see if it precedes the 2026.2 release. If your version is affected, the primary response is to update the software to the latest version provided by JetBrains, which contains the necessary security improvements to handle compilation databases safely.

References

www.jetbrains.com/privacy-security/issues-fixed/

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.