CVE-2026-43898 SandboxJS: Sandbox escape via Function.caller leakage of internal call op
Sandboxed JavaScript code can escape the sandbox and execute arbitrary host code by exploiting Function.caller leakage 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-2026-43898?
CVE-2026-43898 is a critical code injection vulnerability in nyariv SandboxJS, published on 28 May 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 0.9.6, sandbox-defined functions expose Function.caller, allowing sandboxed code to recover the internal LispType.Call runtime callback. That callback can then be invoked with attacker-controlled fake context and obj values to extract blocked host statics, recover the real host Function constructor, and execute arbitrary host JavaScript. This vulnerability is fixed in 0.9.6.
Weakness: CWE-94
Which versions are affected by CVE-2026-43898?
2 open source packages ship an affected version, including @nyariv/sandboxjs. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
@nyariv/sandboxjs npm | All versions | 0.9.6 |
@nyariv/sandboxjs npm | All versions | 0.9.6 |
Products include Nyariv Sandboxjs.
How do I fix CVE-2026-43898?
Upgrade @nyariv/sandboxjs to 0.9.6 or later.
Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.
Is CVE-2026-43898 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-43898 exists.
Other vulnerabilities in nyariv SandboxJS
Sources
Also known as GHSA-g8f2-4f4f-5jqw.