Description
webpack-dev-middleware resolves a request to a local file in getFilenameFromUrl by testing the request pathname against a traversal guard and then slicing it at a fixed character offset. The guard, UP_PATH_REGEXP applied to path.normalize(`./${pathname}`), only matches ".." that stands as a whole path segment, while the containment test is the string comparison pathname.startsWith(publicPathPathname) and the file path is built as path.join(outputPath, pathname.slice(publicPathPathname.length)). When the configured publicPath has no trailing slash, a request such as GET /assets../.env against publicPath /assets yields the pathname /assets../.env, whose only dot-dot sits inside the segment "assets.." and so passes the guard, but the offset slice cuts within that segment and hands "../.env" to path.join, resolving one directory above outputPath. Reading a file from that path requires the middleware to be backed by the physical filesystem, which happens when writeToDisk is true or a custom outputFileSystem is supplied, since the default memfs volume holds only build output. Traversal depth is limited to a single directory because a separately delimited dot-dot segment is collapsed during URL parsing before the guard runs. The default publicPath value of "auto" resolves to "/" and is not affected. This is an incomplete fix for CVE-2024-29180: the guard and offset slice were introduced by that fix and are present in every release from 5.3.4, 6.1.2 and 7.1.0 onward.
Published: 2026-08-24
Score: 8.3 High
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

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History

Mon, 24 Aug 2026 13:30:00 +0000

Type Values Removed Values Added
Description webpack-dev-middleware resolves a request to a local file in getFilenameFromUrl by testing the request pathname against a traversal guard and then slicing it at a fixed character offset. The guard, UP_PATH_REGEXP applied to path.normalize(`./${pathname}`), only matches ".." that stands as a whole path segment, while the containment test is the string comparison pathname.startsWith(publicPathPathname) and the file path is built as path.join(outputPath, pathname.slice(publicPathPathname.length)). When the configured publicPath has no trailing slash, a request such as GET /assets../.env against publicPath /assets yields the pathname /assets../.env, whose only dot-dot sits inside the segment "assets.." and so passes the guard, but the offset slice cuts within that segment and hands "../.env" to path.join, resolving one directory above outputPath. Reading a file from that path requires the middleware to be backed by the physical filesystem, which happens when writeToDisk is true or a custom outputFileSystem is supplied, since the default memfs volume holds only build output. Traversal depth is limited to a single directory because a separately delimited dot-dot segment is collapsed during URL parsing before the guard runs. The default publicPath value of "auto" resolves to "/" and is not affected. This is an incomplete fix for CVE-2024-29180: the guard and offset slice were introduced by that fix and are present in every release from 5.3.4, 6.1.2 and 7.1.0 onward.
Title webpack-dev-middleware Path Traversal via Offset Slice on a Non-Slash-Terminated publicPath
First Time appeared Webpack.js
Webpack.js webpack-dev-middleware
Weaknesses CWE-22
CPEs cpe:2.3:a:webpack.js:webpack-dev-middleware:*:*:*:*:*:*:*:*
Vendors & Products Webpack.js
Webpack.js webpack-dev-middleware
References
Metrics cvssV3_1

{'score': 7.4, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:N/A:N'}

cvssV4_0

{'score': 8.3, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N'}

Subscriptions

Webpack.js Webpack-dev-middleware
cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-08-24T13:12:01.148Z

Reserved: 2026-08-19T20:34:19.724Z

Link: CVE-2026-76844

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-08-24T14:17:02.250

Modified: 2026-08-24T14:17:02.250

Link: CVE-2026-76844

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-24T17:30:06Z

Weaknesses