webpack webpack-dev-middleware up to 5.3.4/6.1.3/7.4.5/8.1.1 URL Parser getFilenameFromUrl path traversal

Summaryinfo

A vulnerability classified as problematic has been found in webpack webpack-dev-middleware up to 5.3.4/6.1.3/7.4.5/8.1.1. This issue affects the function getFilenameFromUrl of the component URL Parser. The manipulation leads to path traversal. This vulnerability is listed as CVE-2026-76844. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability was found in webpack webpack-dev-middleware up to 5.3.4/6.1.3/7.4.5/8.1.1 and classified as problematic. This issue affects the function getFilenameFromUrl of the component URL Parser. The manipulation with an unknown input leads to a path traversal vulnerability. Using CWE to declare the problem leads to CWE-22. The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. Impacted is confidentiality. The summary by CVE is:

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.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-76844 since 08/19/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 08/24/2026). MITRE ATT&CK project uses the attack technique T1006 for this issue.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Type

• Middleware

Vendor

• webpack

Name

• webpack-dev-middleware

Version

• 5.3.0
• 5.3.1
• 5.3.2
• 5.3.3
• 5.3.4
• 6.1.0
• 6.1.1
• 6.1.2
• 6.1.3
• 7.4.0
• 7.4.1
• 7.4.2
• 7.4.3
• 7.4.4
• 7.4.5
• 8.1.0
• 8.1.1

CPE 2.3info

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CPE 2.2info

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CVSSv3info

CVSSv2info

Exploitinginfo

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Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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