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Low, CVSS 2.5amended

esbuild allows arbitrary file read when running the development server on Windows

GHSA-g7r4-m6w7-qqqr

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (esbuild 0.28.1), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • npm esbuild

    Affected
    >= 0.27.3, < 0.28.1
    Fixed in
    0.28.1

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
2.5 · CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N
EPSS
No dated EPSS signal available.
Source description

As published by the source; long descriptions are shortened.

Summary The development server contains a path traversal vulnerability on Windows when serving files from servedir. Due to the use of path.Clean() (which only normalizes forward-slash / separators) instead of a Windows-aware path normalization function, it is possible to craft requests using backslashes (\) that bypass the intended directory containment logic. An attacker can escape the configured servedir root and access arbitrary files on the filesystem. This issue affects Windows environments only. Details The request path is sanitized using: However: - path.Clean() is POSIX-style and only understands / (docs: https://pkg.go.dev/path#Clean) - On Windows, \ is a valid path separator - path.Clean() does not treat \ as a separator Later, the server constructs the absolute path: If queryPath contains sequences such as: path.Clean() will not normalize them, but the Windows filesystem will interpret \ as directory separators when resolving absPath. Because the implementation does not…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-g7r4-m6w7-qqqr

  2. Revision 1 · created ·

    Published from osv record GHSA-g7r4-m6w7-qqqr

Agent brief

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# Patch Next advisory brief: GHSA-g7r4-m6w7-qqqr

Advisory: esbuild allows arbitrary file read when running the development server on Windows
IDs: GHSA-g7r4-m6w7-qqqr
Record: https://patchnext.com/advisories/ghsa-g7r4-m6w7-qqqr (revision 2, source checked 26 Oct 2026, 12:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 2.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: esbuild 0.28.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm esbuild: affected >= 0.27.3, < 0.28.1; fixed in 0.28.1

## Suggested inspection (read-only)
- `npm ls esbuild --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on esbuild.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-g7r4-m6w7-qqqr (OSV record GHSA-g7r4-m6w7-qqqr lists affected ranges: npm esbuild >=0.27.3 <0.28.1 (fixed))
- Verified: https://github.com/advisories/GHSA-g7r4-m6w7-qqqr (GitHub-reviewed advisory GHSA-g7r4-m6w7-qqqr lists affected ranges: npm esbuild >=0.27.3 <0.28.1)

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