CVE-2026-123847 in IntelliJ IDEA
Summary
by MITRE • 11/06/2026
In JetBrains IntelliJ IDEA before 2026.3 command execution was possible via control characters in terminal command completion
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Analysis
by VulDB Data Team • 11/06/2026
The vulnerability identified in versions of JetBrains IntelliJ IDEA prior to version 2026.3 represents a significant security flaw within the integrated development environment's interactive shell integration features. This issue specifically affects the mechanism responsible for handling command line input and auto-completion suggestions when users interact with external terminals or built-in console windows. The core technical deficiency lies in how the application processes control characters embedded within terminal output during the completion process, allowing an attacker to inject arbitrary commands that are subsequently executed by the IDE's underlying system shell without adequate sanitization or validation of the input stream.
From a technical perspective, this flaw is classified under CWE-78 Improper Neutralization of Special Elements used in an OS Command, commonly known as OS Command Injection. The vulnerability arises because IntelliJ IDEA fails to properly escape or filter specific control characters that are part of standard terminal protocol sequences. When a user triggers command completion, the IDE parses the output from the shell to generate suggestions. If this output contains maliciously crafted control character sequences, such as carriage returns followed by newlines and additional commands, the application may interpret these not merely as formatting artifacts but as executable instructions or input data that gets appended to the current command line buffer. This behavior bypasses standard security boundaries because the IDE assumes that terminal output is benign text rather than potential code execution vectors.
The operational impact of this vulnerability allows for remote code execution under specific conditions, particularly when a developer interacts with terminals connected to untrusted sources or compromised build servers. An attacker who can influence the content displayed in an integrated terminal session could trick the user into triggering command completion on maliciously crafted output. Once triggered, the injected commands execute within the context of the IDE process, granting the attacker access to all resources available to that user account. This includes sensitive source code repositories, local environment variables containing API keys or credentials, and connected deployment targets. The severity is exacerbated by the fact that developers often run build tools with elevated privileges or have direct access to production-like environments through their development machines.
This vulnerability aligns closely with MITRE ATT&CK technique T1059 Command and Scripting Interpreter, specifically sub-techniques involving shell commands such as sh or bash. It also relates to T1620 Reflective Code Injection if the control characters are used to manipulate memory structures within the IDE's UI components before execution occurs in the host OS. The attack vector is primarily local but can be triggered remotely via networked terminals, SSH sessions, or CI/CD pipeline outputs that feed into the integrated console. Because the exploitation requires user interaction to trigger completion, it relies on social engineering elements where the victim must actively engage with the compromised terminal output.
Mitigation strategies for this vulnerability involve immediate updates to JetBrains IntelliJ IDEA version 2026.3 or later, which includes patches designed to sanitize control characters and enforce stricter parsing rules during command completion operations. In environments where upgrading is not immediately feasible, administrators should restrict access to integrated terminals by disabling them entirely in untrusted contexts or configuring the IDE to run with restricted shell permissions using tools like rbash or confined shells that limit available commands. Additionally, developers should avoid executing auto-completion on terminal outputs from unknown sources and ensure that their development environments are isolated from critical production systems through proper network segmentation and least-privilege principles. Regular security audits of CI/CD pipeline outputs can also help identify malformed data before it reaches the developer's local IDE instance.