CVE-2026-107353traverse: set() can write to built-in prototypes via an untrusted path

Official description

traverse (npm) versions 0.3.6 through 0.3.9, 0.4.0 through 0.4.6, 0.5.0 through 0.5.2, and 0.6.0 through 0.6.11 allow prototype pollution through set(). When the path passed to set() crosses a primitive value, the next path segment is resolved on that primitive's built-in prototype, so an application that passes an untrusted path to set() lets an attacker add or overwrite properties of String.prototype, Number.prototype, or Boolean.prototype using plain JSON data, for example traverse({ name: 'bob' }).set(['name', '__proto__', 'polluted'], 'yes'). Object.prototype was reachable only with a non-data path segment, such as an object whose toString returns a different value on each call, or through a Proxy that accepts an assignment without storing it. This is fixed in 0.3.10, 0.4.7, 0.5.3, and 0.6.12.

Affected packages & fixed versions

Affected products (as reported)

References

• https://github.com/ljharb/js-traverse/security/advisories/GHSA-rj28-8w7x-jmqc vendor-advisory
• https://github.com/ljharb/js-traverse/commit/81ccab43e379cf42eb2a5f689630f7f79b3d71b8 patch
• https://github.com/ljharb/js-traverse/commit/37a9ebd103d2a259c824c29cdcc3f0dfe1acffce patch