# CVE-2026-39243: decompress allows arbitrary hardlink creation during archive extraction

> Attackers can create arbitrary hardlinks during archive extraction to read or overwrite files on the same filesystem.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 9 Jul 2026
- **Updated:** 10 Jul 2026
- **Also known as:** GHSA-jwp9-9v96-94mx, MINI-7m5j-mr6h-mjjm, MINI-pqvv-vqxg-252f, MINI-v964-8pvp-fh27

## What is CVE-2026-39243?

CVE-2026-39243 is a medium-severity path traversal vulnerability in n/a, published on 9 Jul 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

decompress before 4.2.2 allows arbitrary hardlink creation during archive extraction, enabling file read disclosure and file corruption. When processing hardlink entries (type === 'link'), the x.linkname field from the archive is passed directly to fs.link() without validation (index.js line 113). An attacker can craft an archive with a hardlink entry whose linkname is an absolute path to any file on the same filesystem. This creates a hardlink inside the extraction directory that shares the same inode as the target file, enabling both reading and overwriting the original file's content. Hardlinks are limited to files on the same filesystem and cannot target directories.

Weakness: CWE-59 (Improper Link Resolution Before File Access)

## Which versions are affected by CVE-2026-39243?

2 open source packages ship an affected version, including decompress. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `decompress` | npm | All versions to 4.2.1 | None |
| `decompress` | npm | All versions to 4.2.1 | None |

Products: Decompress Project Decompress.

## How do I fix CVE-2026-39243?

Upgrade to a fixed version.

## Is CVE-2026-39243 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39243 exists.

## Other vulnerabilities in n/a

- [CVE-2020-12265](https://insights.sbomify.com/CVE-2020-12265/): Path Traversal in decompress (critical 9.8)
- [CVE-2026-39246](https://insights.sbomify.com/CVE-2026-39246/): Path traversal in n/a (high 7.5)
- [CVE-2026-39245](https://insights.sbomify.com/CVE-2026-39245/): Path traversal in n/a (medium 6.2)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-39243 and fix it if it is affected.

What it is: CVE-2026-39243 is a medium-severity path traversal vulnerability in n/a, published on 9 Jul 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39243 exists.

Affected packages and fixed versions:
- decompress (npm): affected all versions up to 4.2.1; no fix listed
- decompress (npm): affected all versions up to 4.2.1; 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-2026-39243/ (Markdown: https://insights.sbomify.com/CVE-2026-39243/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-39243
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-39243
- OSV: https://osv.dev/vulnerability/CVE-2026-39243

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-39243/
Summaries are generated and may contain mistakes; the official description above is the record.