{"id":"CVE-2026-76844","summary":"webpack-dev-middleware Path Traversal via Offset Slice on a Non-Slash-Terminated publicPath","details":"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.","aliases":["CVE-2024-29180","GHSA-wr3j-pwj9-hqq6"],"modified":"2026-08-28T11:30:41.385864133Z","published":"2026-08-24T13:12:01.148Z","database_specific":{"cna_assigner":"VulnCheck","cwe_ids":["CWE-22"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/76xxx/CVE-2026-76844.json"},"references":[{"type":"WEB","url":"https://www.npmjs.com/package/webpack-dev-middleware"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/76xxx/CVE-2026-76844.json"},{"type":"ADVISORY","url":"https://github.com/advisories/GHSA-wr3j-pwj9-hqq6"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-76844"},{"type":"ADVISORY","url":"https://www.vulncheck.com/advisories/webpack-dev-middleware-path-traversal-via-offset-slice-on-a-non-slash-terminated-publicpath"},{"type":"PACKAGE","url":"https://github.com/webpack/webpack-dev-middleware"},{"type":"ARTICLE","url":"https://github.com/webpack/webpack-dev-middleware/blob/v8.1.1/src/middleware.js"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/webpack/webpack-dev-middleware","events":[{"introduced":"54e4a9604905898066979a3a918d3d545f761447"},{"last_affected":"4537522597563c5fbe613ee17f91c7e02070c102"},{"introduced":"3d94e45ac602a6f7a904ea5eba2086d7e38240dd"},{"last_affected":"ec97e06f377e593cb40e4a07e81ffd937ea82026"},{"introduced":"07acf80fe1766a199d2f7268a26f356732effc34"},{"last_affected":"be5fb38c664c927e0bbb741ce8483603c32377d3"},{"introduced":"86071ead69e946ada25497d3e281923e885229a4"},{"last_affected":"86071ead69e946ada25497d3e281923e885229a4"}],"database_specific":{"extracted_events":[{"introduced":"6.1.2"},{"last_affected":"6.1.3"},{"introduced":"7.1.0"},{"last_affected":"7.4.5"},{"introduced":"8.0.0"},{"last_affected":"8.1.1"},{"introduced":"5.3.4"},{"last_affected":"5.3.4"}],"source":"AFFECTED_FIELD"}}],"versions":["5.3.4","v8.1.1","v8.1.0","v8.0.4","v8.0.3","v8.0.2","v8.0.1","v8.0.0","v7.4.5","v7.4.4","v7.4.3","v7.4.2","v7.4.1","v7.4.0","v7.3.0","v7.2.1","v7.2.0","v6.1.3","v6.1.2","v7.1.1","v5.3.4","v7.1.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-76844.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"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"}]}