CVE-2026-34208: SandboxJS is a JavaScript sandboxing library

This week

CRITICAL 10.0REMOTEUPGRADE

CVE-2026-34208 is a critical-severity flaw (CVSS 10.0) affecting sandboxjs. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

SandboxJS is a JavaScript sandboxing library. Prior to 0.8.36, SandboxJS blocks direct assignment to global objects (for example Math.random = ...), but this protection can be bypassed through an exposed callable constructor path: this.constructor.call(target, attackerObject). Because this.constructor resolves to the internal SandboxGlobal function and Function.prototype.call is allowed, attacker code can write arbitrary properties into host glob

Why this priority

Critical severity
Public exploit reference
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	10.0 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.6% (top 54%)
CISA exploited list	No
Weakness	CWE-693, CWE-915
Published	2026-04-06
Last modified	2026-10-26

Publisher (CNA): GitHub, Inc. · Vendor: nyariv

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-06 16:16 UTCPublished CVE record published
2026-10-26 22:10 UTCUpdated Record last modified

nyariv sandboxjs UPGRADE

Affected: < 0.8.36

Fixed in: 0.8.36

Safe to downgrade to: no unaffected older release

1. Check installed version

npm ls sandboxjs

2. UPGRADE to 0.8.36

npm install sandboxjs@">=0.8.36"

Exact fixes by distribution

npm · @nyariv/sandboxjs · FIXED · 0.8.36 · vulnerable: < 0.8.36 · source

npm install @nyariv/sandboxjs@">=0.8.36" npm ls @nyariv/sandboxjs

Fedora ELN · openbao · FIXED · 2.6.5-1.eln159 · FEDORA-2026-77adf886ae · source

sudo dnf upgrade --advisory=FEDORA-2026-77adf886ae

Fedora 46 · sugar-turtleart · FIXED · 220-16.fc46 · FEDORA-2026-b79483c788 · source

sudo dnf upgrade --advisory=FEDORA-2026-b79483c788

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Write-up: github.com/nyariv/SandboxJS/security/advisories/GHSA-2gg9-6p7w-6cpj

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-34208?

sandboxjs: upgrade to 0.8.36. Exact commands for each OS are on this page.

Is CVE-2026-34208 being exploited?

CVE-2026-34208 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-34208 affect?

CVE-2026-34208 affects sandboxjs. Severity is critical (CVSS 10.0). SandboxJS is a JavaScript sandboxing library. Prior to 0.8.36, SandboxJS blocks direct assignment to global objects (for example Math.random = ...), but this protection can be bypassed through an exposed callable constructor path: this.cons

How urgent is CVE-2026-34208?

Priority 60/100. Critical severity; Public exploit reference; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-34211 HIGH 7.5 UPGRADE SandboxJS is a JavaScript sandboxing library
CVE-2026-34217 HIGH 7.2 UPGRADE SandboxJS is a JavaScript sandboxing library

References

← Back to latest CVEs