jsii-diff is a command line tool to compare the API differences between two jsii assemblies, and report errors if there are backwards-incompatible changes to the API. An issue exists where specially formatted command line arguments can be used to execute shell commands via this tool.
jsii-diff supports downloading packages to compare directly from NPM, so that you can compare a proposed candidate version of your jsii package with an already-published version, by passing an argument that looks like npm:<package-specifier>. For example:
jsii-diff npm:my-package@latest .
By injecting a ; into the package-specifier part of that command, jsii-diff can be tricked into running shell commands. For example:
jsii-diff "npm:lodash; touch /tmp/123" .
This allows anyone that can control the command-line arguments to jsii-diff to run arbitrary commands with the same permissions as the jsii-diff command itself.
This issue has been addressed in jsii-diff version 1.131.0. We recommend upgrading to the latest version and ensuring any forked or derivative code is patched to incorporate the new fixes.
If you are unable to update, make sure only trusted actors can control the arguments passed to jsii-diff.
If you have any questions or comments about this advisory, AWS asks that you contact AWS Security via the vulnerability reporting page or directly via email to aws-security@amazon.com. Please do not create a public GitHub issue.
{
"severity": "HIGH",
"github_reviewed_at": "2026-08-07T18:15:47Z",
"cwe_ids": [
"CWE-78"
],
"nvd_published_at": null,
"github_reviewed": true
}