How severe is CVE-2026-34208?

CVE-2026-34208 has a CVSS 3.x base score of 10.0, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability low.

Is CVE-2026-34208 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (43rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-34208?

CVE-2026-34208 affects Nyariv Sandboxjs. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-34208?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

Does CVE-2026-34208 have an EU (EUVD) identifier?

Yes. CVE-2026-34208 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-19297.

When was CVE-2026-34208 published?

CVE-2026-34208 was published on 2026-04-06 and last updated on 2026-06-17.

CVE-2026-34208

CVE-2026-34208 is a critical-severity vulnerability in Nyariv Sandboxjs with a CVSS 3.x base score of 10.0. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-693.

Key facts

Severity: Critical (CVSS 3.x base score 10.0)
EPSS exploit prediction: 1% (43rd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-19297
Weakness: CWE-693
Affected product: Nyariv Sandboxjs
Published: 2026-04-06
Last modified: 2026-06-17

Description

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 global objects and persist those mutations across sandbox instances in the same process. This vulnerability is fixed in 0.8.36.

Frequently asked questions

What is CVE-2026-34208?: 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 global objects and persist those mutations across sandbox instances in the same process. This vulnerability is fixed in 0.8.36.
How severe is CVE-2026-34208?: CVE-2026-34208 has a CVSS 3.x base score of 10.0, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability low.
Is CVE-2026-34208 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (43rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-34208?: CVE-2026-34208 affects Nyariv Sandboxjs. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-34208?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2026-34208 have an EU (EUVD) identifier?: Yes. CVE-2026-34208 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-19297.
When was CVE-2026-34208 published?: CVE-2026-34208 was published on 2026-04-06 and last updated on 2026-06-17.

References

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

Affected products (1)

cpe:2.3:a:nyariv:sandboxjs:*:*:*:*:*:node.js:*:*

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