Description

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.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.8",
  "pubDate": "2026-09-11T16:17:49.400Z",
  "pubdate": "2026-09-11T16:17:49.400Z",
  "executiveSummary": "The projen task synthesis component is vulnerable to an OS command injection flaw arising from improper neutralization of special elements used in command execution.\nThis vulnerability affects projen versions prior to 0.103.0.\nThe issue allows context-dependent attackers to execute arbitrary shell commands on a developer's workstation or a CI/CD runner.\nExploitation is achieved by injecting malicious shell metacharacters into project configuration values or repository file names, which are subsequently interpolated into generated task definitions.\nThe risk is significant because the generated task definitions are persisted in the repository as '.projen/tasks.json', meaning malicious payloads can persist even after initial configuration changes.\nSuccessful exploitation grants an attacker the ability to execute code with the permissions of the user running the synthesis process or the CI runner, potentially leading to full system compromise or supply chain poisoning.",
  "technicalDetails": "The root cause of the vulnerability lies in the insecure handling of project configuration values and repository file names during the task synthesis phase of projen.\nProjen functions as a project generation tool that produces task definitions, which are subsequently serialized into the .projen/tasks.json file.\nThe vulnerability occurs because the application fails to adequately sanitize or escape shell metacharacters (e.g., ;, &, |, $()) before incorporating these strings into command strings that are ultimately interpreted by a shell environment.\nAn attacker can exploit this by crafting a project configuration or naming a repository file such that it contains malicious shell sequences. When the projen task synthesis component processes these inputs, it incorrectly embeds them into the generated commands.\nThe attack flow follows a structured path: First, an attacker influences the environment (either via repository metadata or configuration files) to include a malicious shell payload. Second, the developer or CI system executes the projen synthesis process. Third, the synthesis engine reads the tainted input and writes the unneutralized shell command into the .projen/tasks.json file. Finally, when the task is executed—either manually by the developer or automatically by the CI runner—the underlying shell interprets the metacharacters, executing the attacker's arbitrary command.\nThis vulnerability is particularly dangerous because the malicious commands are persisted within the codebase. Even if the project configuration is reverted, the tainted 'tasks.json' file remains in the repository unless explicitly regenerated. This persistent nature increases the likelihood of secondary compromise across various environments, including build servers and development machines.\nThe impact is not limited to the local environment but extends to CI/CD pipelines, potentially allowing for lateral movement, credential theft from environment variables, or the injection of malicious code into build artifacts (supply chain attacks).\nAuthentication and privilege requirements depend on the context of the environment where synthesis occurs; however, in a collaborative repository, the capability to influence configuration or filenames is sufficient to trigger the flaw."
}