CVE-2026-84376: Astro Authorization Bypass From Missing Path-segment Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-376h-93r7-7g6f",
  "modified" : "2026-09-08T21:26:02Z",
  "published" : "2026-09-08T21:26:02Z",
  "aliases" : [ "CVE-2026-84376" ],
  "summary" : "Astro: Authorization bypass from missing path-segment boundary check when stripping the configured base",
  "details" : "## Summary\n\nAstro stripped a configured `base` path from request pathnames using a string-prefix check that did not verify a path-segment boundary. With `base: \"/app\"`, a request to `/appX/admin` was treated as being under the base and resolved internally to the `/admin` route, while middleware still observed the public pathname `/appX/admin`. Middleware that authorizes routes by inspecting `context.url.pathname` could therefore be bypassed.\n\n## Impact\n\nAn unauthenticated remote attacker can bypass pathname-based middleware authorization in applications that:\n\n- Configure a non-root `base`.\n- Protect base-prefixed routes in middleware using `context.url.pathname`.\n\nBecause routing and middleware resolved different effective pathnames, a request such as `/appX/admin` (or other single-character extensions like `/app2/admin` or `/app-/admin`) reached the protected `/admin` route without passing the middleware check that guards `/app/admin`. Astro's authentication guide demonstrates protecting routes in middleware via `context.url.pathname`, so this is a reasonable and expected pattern.\n\n## Affected versions\n\n`astro` <= 7.2.3.\n\n## Patches\n\nFixed in `astro` 7.2.4. Base stripping now requires the pathname to equal the base without its trailing slash, or to be followed by a `/`, so a prefix that does not end on a path-segment boundary is no longer treated as being under the base. Routing and `context.url.pathname` now resolve the same pathname.\n\n## Workarounds\n\nUpgrade to `astro` 7.2.4 or later. As a mitigation before upgrading, avoid relying solely on prefix checks of `context.url.pathname` for authorization, or reject requests whose pathname does not begin with the configured base followed by a path-segment boundary.\n\n## Credits\n\nReported by @Ryoga-exe.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "astro"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "7.2.4"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 7.2.3"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/withastro/astro/security/advisories/GHSA-376h-93r7-7g6f"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-84376"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/withastro/astro/pull/17701"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/withastro/astro/commit/05763a0884aabb1da78a2749d5bb9d41ae620527"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/withastro/astro"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/withastro/astro/releases/tag/astro@7.2.4"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-187" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-09-08T21:26:02Z",
    "nvd_published_at" : "2026-09-02T17:18:00Z"
  }
}