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

High severity GitHub Reviewed Published May 5, 2026 in babel/babel • Updated Jun 8, 2026

Package

npm @babel/plugin-transform-modules-systemjs (npm)

Affected versions

>= 7.12.0, <= 7.29.3
>= 8.0.0-alpha.0, <= 8.0.0-alpha.12

Patched versions

7.29.4
8.0.0-alpha.13

Description

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.

References

@JLHwung JLHwung published to babel/babel May 5, 2026
Published to the GitHub Advisory Database May 8, 2026
Reviewed May 8, 2026
Published by the National Vulnerability Database May 26, 2026
Last updated Jun 8, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
Required
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(3rd percentile)

Weaknesses

Improper Control of Generation of Code ('Code Injection')

The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment. Learn more on MITRE.

Access of Resource Using Incompatible Type ('Type Confusion')

The product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type. Learn more on MITRE.

CVE ID

CVE-2026-44728

GHSA ID

GHSA-fv7c-fp4j-7gwp

Source code

Credits

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