# GHSA-gm9g-2g8v-fvxj: Prototype Pollution in upmerge

> Attackers can pollute object prototypes via the merge function, potentially causing denial of service or remote code execution in applications using this library.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 6 Jun 2019

## What is GHSA-gm9g-2g8v-fvxj?

GHSA-gm9g-2g8v-fvxj is a vulnerability in upmerge, published on 6 Jun 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

All versions of `upmerge` are vulnerable to Prototype Pollution. The merge() function fails to prevent user input to alter an Object's prototype, allowing attackers to modify override properties of all objects in the application. This may lead to Denial of Service or may be chained with other vulnerabilities leading to Remote Code Execution.

## Recommendation

No fix is currently available. Consider using an alternative module until a fix is made available.

## Which versions are affected by GHSA-gm9g-2g8v-fvxj?

2 open source packages ship an affected version, including upmerge.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `upmerge` | npm | All versions to 0.1.8 | None |
| `upmerge` | npm | All versions to 0.1.8 | None |

## How do I fix GHSA-gm9g-2g8v-fvxj?

No fix has been published for GHSA-gm9g-2g8v-fvxj yet. Limit exposure of the affected software until one is available.

## Is GHSA-gm9g-2g8v-fvxj being exploited?

There is no known exploitation of GHSA-gm9g-2g8v-fvxj in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GHSA-gm9g-2g8v-fvxj and fix it if it is affected.

What it is: GHSA-gm9g-2g8v-fvxj is a vulnerability in upmerge, published on 6 Jun 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of GHSA-gm9g-2g8v-fvxj in the wild and no public exploit code.

Affected packages and fixed versions:
- upmerge (npm): affected all versions up to 0.1.8; no fix listed
- upmerge (npm): affected all versions up to 0.1.8; 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/GHSA-gm9g-2g8v-fvxj/ (Markdown: https://insights.sbomify.com/GHSA-gm9g-2g8v-fvxj/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GHSA-gm9g-2g8v-fvxj

---
From sbomify Insights: https://insights.sbomify.com/GHSA-gm9g-2g8v-fvxj/
Summaries are generated and may contain mistakes; the official description above is the record.