Description

Improper neutralization of special elements used in an OS command (CWE-78) in the blueprint resynthesis framework in Amazon Web Services codecatalyst-blueprints before 0.3.156 might allow a user with permission to commit to a repository in the project to execute arbitrary commands in the blueprint resynthesis environment via shell metacharacters in the owner field of a [local] merge strategy entry in a crafted .ownership-file. Version 0.3.156 removes shell interpretation of the owner field, running the command directly rather than through a shell, and rejects values outside an allowlisted command form. This eliminates shell metacharacter command injection. To remediate this issue, users should upgrade to version 0.3.156 or later. No action is required for use of the Amazon CodeCatalyst service. Resynthesis runs in an isolated per-project environment with scoped credentials, and the service applies server-side validation there that rejects [local] merge strategy commands outside a restricted allowlisted form, including for blueprint versions published before 0.3.156.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.0",
  "pubDate": "2026-09-03T18:17:33.190Z",
  "pubdate": "2026-09-03T18:17:33.190Z",
  "executiveSummary": "The Amazon Web Services codecatalyst-blueprints framework is susceptible to an OS command injection vulnerability (CWE-78) prior to version 0.3.156.\nThis vulnerability exists within the blueprint resynthesis process, allowing an authenticated user with repository commit permissions to execute arbitrary system commands within the resynthesis environment.\nThe flaw stems from the improper neutralization of special shell metacharacters within the 'owner' field of a [local] merge strategy entry defined in a '.ownership-file'.\nAn attacker capable of modifying this file can inject malicious payloads that the underlying system processes via a shell, leading to unauthorized command execution.\nWhile the service-side environment of Amazon CodeCatalyst provides some isolation and additional validation, the vulnerability represents a significant security risk for localized deployments or workflows utilizing the blueprint framework.\nExploitation requires the attacker to have existing authorization to commit changes to a project repository, making this an elevation of privilege or unauthorized code execution vector within the CI/CD pipeline.",
  "technicalDetails": "The vulnerability resides in the blueprint resynthesis framework component, specifically in how the application handles configuration inputs from '.ownership-file' files.\nThe root cause is the failure to sanitize or neutralize shell metacharacters within the 'owner' field associated with a '[local]' merge strategy. When the resynthesis engine processes this field, it passes the input directly into a system shell execution context, allowing for command chaining or secondary command execution.\nThe attack flow begins when an attacker, possessing legitimate repository write access, creates or modifies a '.ownership-file' within the project repository. By inserting malicious shell metacharacters (such as backticks, semicolons, or pipe symbols) into the 'owner' field of the '[local]' merge strategy entry, the attacker triggers an injection point.\nDuring the blueprint resynthesis phase, the framework reads the '.ownership-file' and invokes the command associated with the 'owner' field. Because the framework previously relied on shell interpretation, the injected metacharacters are parsed by the shell as legitimate instructions, causing the shell to execute the attacker's payload with the privileges of the resynthesis environment.\nAffected versions are identified as codecatalyst-blueprints before 0.3.156.\nThe post-exploitation impact includes the potential for arbitrary code execution within the isolated resynthesis environment. Although Amazon CodeCatalyst applies server-side validation to mitigate this for hosted services—effectively rejecting unapproved command forms regardless of the blueprint version—the vulnerability remains a concern for the underlying framework code and any environments where this validation might be bypassed or absent.\nRemediation in version 0.3.156 involves transitioning from shell-based execution to direct process invocation. By executing commands without invoking a shell interpreter, the system prevents shell metacharacters from being interpreted as commands. Furthermore, the implementation of an allowlist for the 'owner' field restricts valid inputs to a predefined set of safe command patterns, neutralizing the injection vector entirely."
}