# CVE-2026-23830: SandboxJS has Sandbox Escape via Unprotected AsyncFunction Constructor > Attackers can escape the SandboxJS sandbox by accessing the unprotected AsyncFunction constructor, leading to remote code execution on the host. - **Severity:** Critical 10.0 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 27 Jan 2026 - **Updated:** 28 Jan 2026 - **Also known as:** GHSA-wxhw-j4hc-fmq6 ## What is CVE-2026-23830? CVE-2026-23830 is a critical code injection vulnerability in nyariv SandboxJS, published on 27 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description SandboxJS is a JavaScript sandboxing library. Versions prior to 0.8.26 have a sandbox escape vulnerability due to `AsyncFunction` not being isolated in `SandboxFunction`. The library attempts to sandbox code execution by replacing the global `Function` constructor with a safe, sandboxed version (`SandboxFunction`). This is handled in `utils.ts` by mapping `Function` to `sandboxFunction` within a map used for lookups. However, before version 0.8.26, the library did not include mappings for `AsyncFunction`, `GeneratorFunction`, and `AsyncGeneratorFunction`. These constructors are not global properties but can be accessed via the `.constructor` property of an instance (e.g., `(async () => {}).constructor`). In `executor.ts`, property access is handled. When code running inside the sandbox accesses `.constructor` on an async function (which the sandbox allows creating), the `executor` retrieves the property value. Since `AsyncFunction` was not in the safe-replacement map, the `executor` returns the actual native host `AsyncFunction` constructor. Constructors for functions in JavaScript (like `Function`, `AsyncFunction`) create functions that execute in the global scope. By obtaining the host `AsyncFunction` constructor, an attacker can create a new async function that executes entirely outside the sandbox context, bypassing all restrictions and gaining full access to the host environment (Remote Code Execution). Version 0.8.26 patches this vulnerability. Weakness: CWE-94 (Improper Control of Generation of Code), CWE-913 (Improper Control of Dynamically-Managed Code Resources), CWE-693 (Protection Mechanism Failure) ## Which versions are affected by CVE-2026-23830? 2 open source packages ship an affected version, including @nyariv/sandboxjs. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `@nyariv/sandboxjs` | npm | All versions | 0.8.26 | | `@nyariv/sandboxjs` | npm | All versions | 0.8.26 | Products: Nyariv Sandboxjs. ## How do I fix CVE-2026-23830? Upgrade @nyariv/sandboxjs to 0.8.26 or later. ## Is CVE-2026-23830 being exploited? It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-23830 exists. Public exploit code: - https://github.com/Galaxy-sc/CVE-2026-23830-SandBreak (github_poc): https://github.com/Galaxy-sc/CVE-2026-23830-SandBreak ## Other vulnerabilities in nyariv SandboxJS - [CVE-2026-43898](https://insights.sbomify.com/CVE-2026-43898/): SandboxJS: Sandbox escape via Function.caller leakage of internal call op (critical 10.0) - [CVE-2026-34208](https://insights.sbomify.com/CVE-2026-34208/): SandboxJS: Sandbox integrity escape (critical 10.0) - [CVE-2026-26954](https://insights.sbomify.com/CVE-2026-26954/): SandboxJS has a Sandbox Escape (critical 10.0) - [CVE-2026-25520](https://insights.sbomify.com/CVE-2026-25520/): SandboxJS has a Sandbox Escape (critical 10.0) - [CVE-2026-25586](https://insights.sbomify.com/CVE-2026-25586/): SandboxJS has a Sandbox Escape via Prototype Whitelist Bypass and Host Prototype Pollution (critical 10.0) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-23830 and fix it if it is affected. What it is: CVE-2026-23830 is a critical code injection vulnerability in nyariv SandboxJS, published on 27 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-23830 exists. Affected packages and fixed versions: - @nyariv/sandboxjs (npm): affected all versions; fixed in 0.8.26 - @nyariv/sandboxjs (npm): affected all versions; fixed in 0.8.26 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-23830/ (Markdown: https://insights.sbomify.com/CVE-2026-23830/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23830 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23830 - OSV: https://osv.dev/vulnerability/CVE-2026-23830 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-23830/ Summaries are generated and may contain mistakes; the official description above is the record.