Security Digest · Vulnerability record
CVE-2026-26954: SandboxJS affected by a Sandbox Escape
SandboxJS is a JavaScript sandboxing library.
CVSS 10.0 Critical EPSS 0.6% · p49
Should you act?
Critical and remotely reachable
No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 0.6%, percentile 49: FIRST’s model estimates a 0.6% chance of exploitation activity in the next 30 days, higher than 49% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes
@nyariv/sandboxjs(npm) <= 0.8.33, fixed in 0.8.34. Check your lockfile, including transitive dependencies.
What it is
SandboxJS is a JavaScript sandboxing library. Prior to 0.8.34, it is possible to obtain arrays containing Function, which allows escaping the sandbox. Given an array containing Function, and Object.fromEntries, it is possible to construct {[p]: Function} where p is any constructible property. This vulnerability is fixed in 0.8.34.
From the GitHub advisory
Summary
It is possible to obtain arrays containing Function, which allows escaping the sandbox.
Details
There are various ways to get an array containing Function, e.g.
Given an array containing Function, and Object.fromEntries, it is possible to construct {[p]: Function} where p is any constructible property. This can be used to escape the sandbox.
Weakness type: CWE-94.
Product: @nyariv/sandboxjs (npm) · Assigned by: GitHub_M · Published: 2026-03-13
Affected and fixed versions
| Ecosystem | Package | Vulnerable | First fixed |
|---|---|---|---|
| npm | @nyariv/sandboxjs | <= 0.8.33 | 0.8.34 |
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| nyariv | SandboxJS | < 0.8.34 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_M | 3.1 | 10 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H |
| GitHub | 3.1 | 10.0 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Privileges required: none (no login)
- User interaction: none
- Scope: changed (can affect other components)
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc, automatable yes, technical impact total.
- FIRST EPSS (model of 2026-10-21): 0.62% probability of exploitation activity in the next 30 days; percentile 49.
Timeline
- — CVE record published by GitHub_M
- — GitHub-reviewed advisory GHSA-6r9f-759j-hjgv published (critical)
- — CVE record last updated
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vulnerability records
- GitHub Advisory GHSA-6r9f-759j-hjgv github.com
- CVE.org record CVE-2026-26954 cve.org
- NVD entry CVE-2026-26954 nvd.nist.gov
Other references from the CVE record and advisory
- github.com github.com
- github.com github.com
- github.com github.com