expand-object Vulnerable to Prototype Pollution via the expand() Function

Exploitation

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

CVSS 4.0

5.5 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X · score source

EPSS

• CVE-2025-3197: 0.42% estimated exploitation activity in the next 30 days; percentile 36.68 (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.

Versions of the package expand-object from 0.0.0 to 0.4.2 are vulnerable to Prototype Pollution in the expand() function in index.js. This function expands the given string into an object and allows a nested property to be set without checking the provided keys for sensitive properties like proto.

Published by the source

4 Apr 2025, 06:34 UTC

Last modified by the source

4 Apr 2025, 19:27 UTC

Source last checked

26 Oct 2026, 12:36 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-4vjr-hfpp-2m7w

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-4vjr-hfpp-2m7w

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2025-3197

Advisory: expand-object Vulnerable to Prototype Pollution via the expand() Function
IDs: CVE-2025-3197, GHSA-4vjr-hfpp-2m7w
Record: https://patchnext.com/advisories/cve-2025-3197 (revision 3, source checked 26 Oct 2026, 12:36 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm expand-object: affected <= 0.4.2

## Suggested inspection (read-only)
- `npm ls expand-object --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on expand-object.
- 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-4vjr-hfpp-2m7w (OSV record GHSA-4vjr-hfpp-2m7w lists affected ranges: npm expand-object >=0 <=0.4.2)
- Verified: https://github.com/advisories/GHSA-4vjr-hfpp-2m7w (GitHub-reviewed advisory GHSA-4vjr-hfpp-2m7w lists affected ranges: npm expand-object >=0 <=0.4.2)

Commands are suggestions: review each one before running it.