CVE-2026-44594
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedesm.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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceesm.sh versions 137 and earlier contain a Local File Inclusion vulnerability in the esbuild plugin's handling of the 'browser' field in package.json. Attackers can publish malicious npm packages that cause the CDN server to read and return arbitrary files from the host filesystem during the build process by manipulating path traversal sequences in the browser field.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify esm.sh versionCheck the version of esm.sh installed or running in your environment. This may be found in package.json dependencies, a running service version endpoint, or the esm.sh server binary/version file.Affected if The installed version is 137 or earlier
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Confirm esbuild plugin is activeVerify that the esbuild plugin is enabled in your esm.sh configuration or build pipeline. This plugin handles the processing of package.json files during npm package imports.Affected if The esbuild plugin processes package.json files from npm packages in your environment
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Determine if untrusted npm packages are processedReview whether your esm.sh instance imports or builds packages from untrusted or public npm sources. The vulnerability is triggered when processing the 'browser' field from package.json during the build process.Affected if Your esm.sh instance processes npm packages where the 'browser' field could be manipulated by package publishers
You are affected if your esm.sh version is 137 or earlier and your environment processes npm packages through the esbuild plugin, allowing untrusted package.json files with manipulated browser fields to trigger the path traversal vulnerability.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataUpgrade esm.sh to version 138 or later to obtain the patch. As an interim measure, implement strict path validation on the browser field processing to prevent directory traversal before the fix can be applied.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA3.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-44594 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-44594 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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