# CVE-2025-3197: expand-object Vulnerable to Prototype Pollution via the expand() Function

> Prototype pollution in expand-object allows attackers to modify object prototypes, potentially leading to code execution or privilege escalation.

- **Severity:** Medium 6.9 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 4 Apr 2025
- **Updated:** 4 Apr 2025
- **Also known as:** GHSA-4vjr-hfpp-2m7w

## What is CVE-2025-3197?

CVE-2025-3197 is a medium-severity vulnerability in expand-object, published on 4 Apr 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Versions of the package expand-object from 0.0.0 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__.

Weakness: CWE-1321 (Improperly Controlled Modification of Object Prototype Attributes)

## Which versions are affected by CVE-2025-3197?

2 open source packages ship an affected version, including expand-object.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `expand-object` | npm | All versions to 0.4.2 | None |
| `expand-object` | npm | All versions to 0.4.2 | None |

## How do I fix CVE-2025-3197?

No fix has been published for CVE-2025-3197 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-3197 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-3197 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-3197 and fix it if it is affected.

What it is: CVE-2025-3197 is a medium-severity vulnerability in expand-object, published on 4 Apr 2025. 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-2025-3197 exists.

Affected packages and fixed versions:
- expand-object (npm): affected all versions up to 0.4.2; no fix listed
- expand-object (npm): affected all versions up to 0.4.2; no fix listed

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-2025-3197/ (Markdown: https://insights.sbomify.com/CVE-2025-3197/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-3197
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-3197
- OSV: https://osv.dev/vulnerability/CVE-2025-3197

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-3197/
Summaries are generated and may contain mistakes; the official description above is the record.