Anthropic Sandbox Runtime Incorrectly Implemented Network Sandboxing

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

1.8 · CVSS:4.0/AV:L/AC:L/AT:P/PR:H/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2025-66479: 0.16% estimated exploitation activity in the next 30 days; percentile 5.57 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Due to a bug in sandboxing logic, sandbox-runtime did not properly enforce a network sandbox if the sandbox policy did not configure any allowed domains. This could allow sandboxed code to make network requests outside of the sandbox. A patch for this was released in v0.0.16. Thank you to https://github.com/bendrucker for reporting this issue!

Published by the source

4 Dec 2025, 16:55 UTC

Last modified by the source

5 Dec 2025, 12:42 UTC

Source last checked

26 Oct 2026, 12:41 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-9gqj-5w7c-vx47

2. Revision 2 · amended · 24 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-9gqj-5w7c-vx47

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# Patch Next advisory brief: CVE-2025-66479

Advisory: Anthropic Sandbox Runtime Incorrectly Implemented Network Sandboxing
IDs: CVE-2025-66479, GHSA-9gqj-5w7c-vx47
Record: https://patchnext.com/advisories/cve-2025-66479 (revision 3, source checked 26 Oct 2026, 12:41 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 1.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @anthropic-ai/sandbox-runtime 0.0.16. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @anthropic-ai/sandbox-runtime: affected < 0.0.16; fixed in 0.0.16

## Suggested inspection (read-only)
- `npm ls @anthropic-ai/sandbox-runtime --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @anthropic-ai/sandbox-runtime.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-9gqj-5w7c-vx47 (OSV record GHSA-9gqj-5w7c-vx47 lists affected ranges: npm @anthropic-ai/sandbox-runtime >=0 <0.0.16 (fixed))
- Verified: https://github.com/advisories/GHSA-9gqj-5w7c-vx47 (GitHub-reviewed advisory GHSA-9gqj-5w7c-vx47 lists affected ranges: npm @anthropic-ai/sandbox-runtime >=0 <0.0.16)

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