{"id":"CVE-2026-44573","aliases":["GHSA-36qx-fr4f-26g5"],"url":"https://o3.security/vulnerability/CVE-2026-44573","summary":"Next.js: Middleware / Proxy bypass in Pages Router applications using i18n","details":"### Impact\n\nApplications using the Pages Router with `i18n` configured and middleware/proxy-based authorization can allow unauthorized access to protected page data through locale-less `/_next/data/<buildId>/<page>.json` requests. In affected configurations, middleware does not run for the unprefixed data route, allowing an attacker to retrieve SSR JSON for protected pages without passing the intended authorization checks.\n\n### Fix\nThe matcher logic was updated to perform the same match as it would on a non-i18n data route.\n\n### Workarounds\n\nIf you cannot upgrade immediately, enforce authorization in the page's server-side data path instead of relying solely on middleware.","published":"2026-05-13T16:48:16.218Z","modified":"2026-08-15T04:07:13.008249534Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"},"epss":{"score":0.0062,"percentile":0.47009,"asOf":"2026-08-24"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"next","fixedVersion":"15.5.16"},{"ecosystem":"npm","name":"next","fixedVersion":"16.2.5"}],"fix":null,"references":[{"type":"WEB","url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-44573.json"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:34608"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:37272"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:40974"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:54435"},{"type":"ADVISORY","url":"https://access.redhat.com/security/cve/CVE-2026-44573"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/44xxx/CVE-2026-44573.json"},{"type":"ADVISORY","url":"https://github.com/vercel/next.js/security/advisories/GHSA-36qx-fr4f-26g5"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-44573"},{"type":"REPORT","url":"https://bugzilla.redhat.com/show_bug.cgi?id=2477199"},{"type":"PACKAGE","url":"https://github.com/vercel/next.js"},{"type":"WEB","url":"https://github.com/vercel/next.js/releases/tag/v15.5.16"},{"type":"WEB","url":"https://github.com/vercel/next.js/releases/tag/v16.2.5"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-15T04:07:13.008249534Z"}}