Security Digest · Vulnerability record
CVE-2026-25142: SandboxJS Vulnerable to Prototype Pollution -> Sandbox Escape -> RCE
SandboxJS is a JavaScript sandboxing library.
CVSS 10.0 Critical EPSS 1.2% · p69
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.
- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 1.2%, percentile 69: FIRST’s model estimates a 1.2% chance of exploitation activity in the next 30 days, higher than 69% of all scored CVEs (moderate). 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) <= 0.8.26, fixed in 0.8.27. Check your lockfile, including transitive dependencies.
What it is
SandboxJS is a JavaScript sandboxing library. Prior to 0.8.27, SanboxJS does not properly restrict lookupGetter which can be used to obtain prototypes, which can be used for escaping the sandbox / remote code execution. This vulnerability is fixed in 0.8.27.
From the GitHub advisory
Summary
SandboxJS does not properly restrict lookupGetter which can be used to obtain prototypes, which can be used for escaping the sandbox / remote code execution.
Details
https://github.com/nyariv/SandboxJS/blob/f212a38fb5a6d4bc2bc2e2466c0c011ce8d41072/src/executor.ts#L368-L398
The Object prototype which contains lookupGetter is properly protected, but the special case for accessing function properties bypasses the prototype chain checks including the root Object prototype.
Weakness type: CWE-94, CWE-1321.
Product: @nyariv/sandboxjs (npm) · Assigned by: GitHub_M · Published: 2026-02-02
Affected and fixed versions
| Ecosystem | Package | Vulnerable | First fixed |
|---|---|---|---|
| npm | @nyariv/sandboxjs | <= 0.8.26 | 0.8.27 |
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| nyariv | SandboxJS | < 0.8.27 |
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 none, automatable yes, technical impact total.
- FIRST EPSS (model of 2026-10-21): 1.23% probability of exploitation activity in the next 30 days; percentile 69.
Timeline
- — CVE record published by GitHub_M
- — GitHub-reviewed advisory GHSA-9p4w-fq8m-2hp7 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-9p4w-fq8m-2hp7 github.com
- CVE.org record CVE-2026-25142 cve.org
- NVD entry CVE-2026-25142 nvd.nist.gov
Other references from the CVE record and advisory
- github.com github.com
- github.com github.com
- github.com github.com