webpack-dev-middleware vulnerable to Path Traversal via non-slash-terminated publicPath
[!IMPORTANT] CVE-2026-76844 was assigned and published for this issue by VulnCheck on 2026-08-24 without prior coordination with the webpack maintainers or the OpenJS Foundation, which holds the CVE Numbering Authority scope for webpack projects. Neither the maintainers nor the OpenJS CNA were notified before publication, and no fix was available at that time. This advisory is the coordinated record produced by the webpack maintainers and the OpenJS Foundation CNA.
Impact
webpack-dev-middleware resolves a request to a local file in getFilenameFromUrl. When the configured publicPath has no trailing slash (for example /assets), a request that shares that prefix without being under it (for example /assets../secret) still passes the containment check, and the .. guard does not catch it because it runs on the path before the publicPath prefix is stripped. The stripped remainder then escapes the configured output directory once joined, so an unauthenticated request can read files outside the output root. Applications serving webpack-dev-middleware (directly or via webpack-dev-server) with a publicPath that does not end in a slash are affected. A development server reachable on the network can be attacked with a single request and no victim interaction.
Patches
Patched in webpack-dev-middleware 8.3.0. There is no backport to the 5.x, 6.x, or 7.x lines; users on those lines should upgrade to 8.3.0 or later.
Workarounds
Configure publicPath with a trailing slash (for example /assets/ instead of /assets), or upgrade to a patched version.
References
- CVE-2024-29180 (GHSA-wr3j-pwj9-hqq6), the earlier path traversal in the same component that this issue bypasses.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | webpack-dev-middleware | >= 8.0.0, < 8.3.0, < 7.4.6 | 8.3.0, 7.4.6 |
References
- https://github.com/webpack/webpack-dev-middleware/security/advisories/GHSA-g84c-rxfj-3j2c
- https://nvd.nist.gov/vuln/detail/CVE-2026-76844
- https://github.com/webpack/webpack-dev-middleware/pull/2404
- https://github.com/webpack/webpack-dev-middleware/commit/13344e78b26d88fe9b7c8381a3860e248a52359b
- https://github.com/webpack/webpack-dev-middleware/commit/cefccbac330c29052fc6dffe85fd292ea2ac782b
- https://github.com/advisories/GHSA-wr3j-pwj9-hqq6
- https://github.com/webpack/webpack-dev-middleware
- https://github.com/webpack/webpack-dev-middleware/blob/v8.1.1/src/middleware.js
- https://github.com/webpack/webpack-dev-middleware/releases/tag/v7.4.6
- https://github.com/webpack/webpack-dev-middleware/releases/tag/v8.3.0
- https://www.vulncheck.com/advisories/webpack-dev-middleware-path-traversal-via-offset-slice-on-a-non-slash-terminated-publicpath
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:N/A:N- Weakness (CWE)
CWE-22- Platform
- npm
- Package
webpack-dev-middleware- Disclosed
- 29.09.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-g84c-rxfj-3j2c - CC BY 4.0
Vulnerability history: webpack-dev-middleware
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 2
- First → latest
- 03.2024 09.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 2
Disclosures per year
- 2024: 1
- 2025: 0
- 2026: 1
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