CVE-2026-44728: Improper Control of Generation of Code when compiling specifically crafted malicious code with @babel/plugin-transform-modules-systemjs

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/plugin-transform-modules-systemjs@7.29.4.

Babel also released @babel/preset-env@7.29.5, 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.