CVE-2026-89066 in Projen
Summary
by MITRE • 09/11/2026
Improper neutralization of special elements used in an OS command in the task synthesis component in projen before 0.103.0 might allow context-dependent attackers to execute arbitrary commands on a developer workstation or continuous integration runner via shell metacharacters in project configuration values and repository file names that are interpolated into generated task definitions.
To remediate this issue, users should upgrade to version 0.103.0 and then re-synthesize the project so that .projen/tasks.json is regenerated with the corrected task definitions. Upgrading alone is not sufficient because the generated task definition file is committed to the repository.
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Analysis
by VulDB Data Team • 09/11/2026
The vulnerability identified as Improper Neutralization of Special Elements Used in an OS Command represents a critical security flaw within the projen project synthesis component prior to version 0.103.0. This issue stems from inadequate input validation and sanitization mechanisms when handling user-supplied data that is subsequently interpolated into operating system command strings. Specifically, the task synthesis logic fails to properly escape or neutralize shell metacharacters present in project configuration values and repository file names. When these unsanitized inputs are processed, they can alter the intended structure of the generated OS commands, allowing context-dependent attackers to inject arbitrary commands that execute with the privileges of the user running the projen synthesis process.
From a technical perspective, this vulnerability exploits the way shell interpreters parse command lines. If an attacker controls or influences project configuration values such as task names, script arguments, or even repository file paths used in generated tasks, they can introduce characters like semicolons, pipes, ampersands, or backticks. These metacharacters allow for command chaining and substitution, effectively breaking out of the intended context of a single command into multiple commands or subshells. Since projen is often run during development workflows on developer workstations or within continuous integration runners, the impact extends beyond simple data leakage to full remote code execution capabilities under the user's account.
The operational impact of this vulnerability is severe due to its potential for widespread exploitation in modern software engineering pipelines. Developer workstations are frequently used as build agents and may contain sensitive credentials, source code repositories, and development tools that could be compromised if an attacker gains command execution privileges. Similarly, continuous integration runners often operate with elevated permissions or access to production-like environments. An attack vector involving a maliciously crafted project configuration file submitted via pull request or merged into the main branch could trigger automatic synthesis processes on CI systems, leading to unauthorized data exfiltration, installation of malware, or pivoting to other internal network resources. This aligns closely with CWE-78 Improper Neutralization of Special Elements used in an OS Command and maps to ATT&CK techniques such as T1059 Command and Scripting Interpreter for initial execution and potentially T1620 Reflective Code Loading if further exploitation steps are taken within the compromised environment.
To remediate this vulnerability, organizations must upgrade projen to version 0.103.0 or later immediately. It is crucial to understand that upgrading the tool alone does not resolve existing vulnerabilities in already generated project files because the task definitions are persisted as static JSON artifacts committed to the repository. Therefore, after upgrading the dependency, developers and CI systems must explicitly re-synthesize all affected projects. This process regenerates the .projen/tasks.json file with corrected logic that properly neutralizes special elements before they reach the OS command layer. Failure to perform this regeneration step leaves existing task definitions vulnerable until they are manually or automatically updated through a synthesis cycle, leaving a window of exposure for potential attackers targeting legacy configurations in active repositories.