CVE-2026-34211
HIGHCVE-2026-34211 is a high-severity (CVSS 7.5) CWE-674 vulnerability in nyariv sandboxjs. O3 Security detects and blocks CVE-2026-34211 exploitation at runtime via eBPF exploit-chain detection and L7 egress monitoring, even on unpatched systems.
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.…
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.
Affected Products
sandboxjsnyarivDetection & mitigation playbook
Vendor / applianceDetect
Inventory every nyariv sandboxjs deployment and check each version against the affected-products list above. Because the exploit targets the running system rather than your application code, also watch for exploitation at the network and runtime layer — O3 flags the exploit behaviour from runtime telemetry and egress traffic even before a vulnerable build is confirmed.
Fix
Apply the nyariv sandboxjs security patch or hotfix for CVE-2026-34211 on the affected version, following the vendor advisory for your exact build.
Workarounds
Cut exposure now: restrict the management/admin interface to trusted networks, segment the device, and apply the vendor's recommended configuration mitigations and any WAF/IPS signature. O3's runtime protection blocks the exploit chain at execution, holding the line on unpatched or end-of-life systems until you can patch.
How O3 protects you
O3 detects and blocks CVE-2026-34211 exploitation at runtime: eBPF exploit-chain detection, plus L7 egress monitoring that catches the post-exploitation callback and severs the attacker's outbound channel.
Tailored to CVE-2026-34211. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-34211 being exploited in your environment?
O3's eBPF runtime sensors and L7 egress monitoring detect and block the CVE-2026-34211 exploit chain at execution — protecting unpatched and end-of-life systems until the vendor patch is applied.