@babel/plugin-transform-modules-systemjs generates arbitrary code when compiling malicious input

Impact

Using Babel to compile code that was specifically crafted by an attacker can cause Babel to generate output code that executes arbitrary code.

Known affected plugins are:

• @babel/plugin-transform-modules-systemjs
• @babel/preset-env when using the modules: "systemjs" option, as it delegates to @babel/plugin-transform-modules-systemjs

No other plugins under the @babel namespace are impacted.

Users that only compile trusted code are not impacted.

Patches

The vulnerability has been fixed in @babel/[email protected].

Babel also released @babel/[email protected], updating its @babel/plugin-transform-modules-systemjs dependency, to simplify forcing the update if you are using @babel/preset-env directly.

Workarounds

• Pin @babel/parser to v7.11.5. The downgrade will completely disable string module name parsing, but it would also disable other new language features and the build pipeline may fail as a result. Only do so if you are working on a legacy codebase and can not upgrade @babel/plugin-transform-modules-systemjs to v7.29.4.
• Do not use the modules: "systemjs" option, migrate the codebase to native ES Modules or any other module formats.

Credits

Babel thanks Daniel Cervera for reporting the vulnerability.