# CVE-2026-44594: esm.sh: Path Traversal via package.json browser field allows reading arbitrary server files

> Attackers can read arbitrary server files by publishing a malicious npm package with a crafted browser field in package.json.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 May 2026
- **Updated:** 28 May 2026
- **Also known as:** GHSA-rg65-45m7-hq57, GO-2026-5620

## What is CVE-2026-44594?

CVE-2026-44594 is a high-severity path traversal vulnerability in esm-dev esm.sh, published on 28 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

esm.sh is a no-build content delivery network (CDN) for web development. In 137 and earlier, a Local File Inclusion (LFI) vulnerability exists in the esbuild plugin's handling of the browser field in package.json. An attacker can publish an npm package that causes the server to read and return arbitrary files from the host filesystem during the build process.

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-44594?

3 open source packages ship an affected version, including github.com/esm-dev/esm.sh.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/esm-dev/esm.sh` | Go | All versions | 0.0.0-20250616164159-0593516c4cfa |
| `github.com/esm-dev/esm.sh` | Go | All versions | 0.0.0-20250616164159-0593516c4cfa |
| `github.com/esm-dev/esm.sh` | Go | All versions | 0.0.0-20250616164159-0593516c4cfa |

## How do I fix CVE-2026-44594?

Upgrade github.com/esm-dev/esm.sh to 0.0.0-20250616164159-0593516c4cfa or later.

## Is CVE-2026-44594 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-44594 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-44594 and fix it if it is affected.

What it is: CVE-2026-44594 is a high-severity path traversal vulnerability in esm-dev esm.sh, published on 28 May 2026. 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-2026-44594 exists.

Affected packages and fixed versions:
- github.com/esm-dev/esm.sh (Go): affected all versions; fixed in 0.0.0-20250616164159-0593516c4cfa
- github.com/esm-dev/esm.sh (Go): affected all versions; fixed in 0.0.0-20250616164159-0593516c4cfa
- github.com/esm-dev/esm.sh (Go): affected all versions; fixed in 0.0.0-20250616164159-0593516c4cfa

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-2026-44594/ (Markdown: https://insights.sbomify.com/CVE-2026-44594/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-44594
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-44594
- OSV: https://osv.dev/vulnerability/CVE-2026-44594

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-44594/
Summaries are generated and may contain mistakes; the official description above is the record.