CVE-2026-34211 SandboxJS: Stack overflow DoS via deeply nested expressions in recursive descent parser

What is CVE-2026-34211?

CVE-2026-34211 is a medium-severity denial of service 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, the @nyariv/sandboxjs parser contains unbounded recursion in the restOfExp function and the lispify/lispifyExpr call chain. An attacker can crash any Node.js process that parses untrusted input by supplying deeply nested expressions (e.g., ~2000 nested parentheses), causing a RangeError: Maximum call stack size exceeded that terminates the process. This vulnerability is fixed in 0.8.36.

Weakness: CWE-674

Which versions are affected by CVE-2026-34211?

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

Products include Nyariv Sandboxjs.

How do I fix CVE-2026-34211?

Upgrade @nyariv/sandboxjs to 0.8.36 or later.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-34211 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-34211 exists.

Other vulnerabilities in nyariv SandboxJS

• CVE-2026-43898 SandboxJS: Sandbox escape via Function.caller leakage of internal call op Critical 10.0
• CVE-2026-34208 SandboxJS: Sandbox integrity escape Critical 10.0
• CVE-2026-26954 SandboxJS has a Sandbox Escape Critical 10.0
• CVE-2026-25520 SandboxJS has a Sandbox Escape Critical 10.0
• CVE-2026-25586 SandboxJS has a Sandbox Escape via Prototype Whitelist Bypass and Host Prototype Pollution Critical 10.0

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-8pfc-jjgw-6g26.