{"apiVersion":"1.0","identifier":"CVE-2026-76844","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.","publishedAt":"2026-08-24T14:17:02","lastModifiedAt":"2026-08-26T19:17:05","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-76844","cvssScore":7.4,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:N/A:N","epssProbability":0.00371,"riskScore":0.76,"affectedProduct":"webpack-dev-middleware","affectedVersions":"unknown","vulnerabilityType":"Library","operatingSystems":[],"links":{"self":"https://www.redsauce.net/api/cves/CVE-2026-76844","webPages":{"es":"https://www.redsauce.net/es/cves/CVE-2026-76844","en":"https://www.redsauce.net/en/cves/CVE-2026-76844","fr":"https://www.redsauce.net/fr/cves/CVE-2026-76844","pt":"https://www.redsauce.net/pt/cves/CVE-2026-76844","de":"https://www.redsauce.net/de/cves/CVE-2026-76844","sk":"https://www.redsauce.net/sk/cves/CVE-2026-76844","el":"https://www.redsauce.net/el/cves/CVE-2026-76844"},"source":"https://nvd.nist.gov/vuln/detail/CVE-2026-76844"}}