CVE-2026-34217 SandboxJS has a Sandbox Escape via Prop Object Leak in New Handler

Medium 6.9 Published 6 Apr 2026 Updated 6 Apr 2026

Untrusted code can leak internal interpreter objects via the new operator, bypassing sandbox scope protections in SandboxJS.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2026-34217?

CVE-2026-34217 is a medium-severity vulnerability in nyariv SandboxJS, published on 6 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

SandboxJS is a JavaScript sandboxing library. Prior to 0.8.36, a scope modification vulnerability exists in @nyariv/sandboxjs. The vulnerability allows untrusted sandboxed code to leak internal interpreter objects through the new operator, exposing sandbox scope objects in the scope hierarchy to untrusted code; an unexpected and undesired exploit. While this could allow modifying scopes inside the sandbox, code evaluation remains sandboxed and prototypes remain protected throughout the execution. This vulnerability is fixed in 0.8.36.

Weakness: CWE-668

Which versions are affected by CVE-2026-34217?

2 open source packages ship an affected version, including @nyariv/sandboxjs. It affects 1 product.

Package	Affected	Fixed in
`@nyariv/sandboxjs` npm	All versions	`0.8.36`
`@nyariv/sandboxjs` npm	All versions	`0.8.36`

Products include Nyariv Sandboxjs.

How do I fix CVE-2026-34217?

Upgrade @nyariv/sandboxjs to 0.8.36 or later.

Is CVE-2026-34217 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-34217 exists.

Sources

Also known as GHSA-hg73-4w7g-q96w.