{"id":"GHSA-v5gw-mw7f-84px","summary":"Starlette has Path Traversal vulnerability in StaticFiles","details":"### Summary\nWhen using `StaticFiles`, if there's a file or directory that starts with the same name as the `StaticFiles` directory, that file or directory is also exposed via `StaticFiles` which is a path traversal vulnerability.\n\n### Details\nThe root cause of this issue is the usage of `os.path.commonprefix()`:\nhttps://github.com/encode/starlette/blob/4bab981d9e870f6cee1bd4cd59b87ddaf355b2dc/starlette/staticfiles.py#L172-L174\n\nAs stated in the Python documentation (https://docs.python.org/3/library/os.path.html#os.path.commonprefix) this function returns the longest prefix common to paths.\n\nWhen passing a path like `/static/../static1.txt`, `os.path.commonprefix([full_path, directory])` returns `./static` which is the common part of `./static1.txt` and `./static`, It refers to `/static/../static1.txt` because it is considered in the staticfiles directory. As a result, it becomes possible to view files that should not be open to the public.\n\nThe solution is to use `os.path.commonpath` as the Python documentation explains that `os.path.commonprefix` works a character at a time, it does not treat the arguments as paths.\n\n### PoC\nIn order to reproduce the issue, you need to create the following structure:\n\n```\n├── static\n│   ├── index.html\n├── static_disallow\n│   ├── index.html\n└── static1.txt\n```\n\nAnd run the `Starlette` app with:\n\n```py\nimport uvicorn\nfrom starlette.applications import Starlette\nfrom starlette.routing import Mount\nfrom starlette.staticfiles import StaticFiles\n\n\nroutes = [\n    Mount(\"/static\", app=StaticFiles(directory=\"static\", html=True), name=\"static\"),\n]\n\napp = Starlette(routes=routes)\n\n\nif __name__ == \"__main__\":\n    uvicorn.run(app, host=\"0.0.0.0\", port=8000)\n```\n\nAnd running the commands:\n\n```shell\ncurl --path-as-is 'localhost:8000/static/../static_disallow/'\ncurl --path-as-is 'localhost:8000/static/../static1.txt'\n```\nThe `static1.txt` and the directory `static_disallow` are exposed.\n\n### Impact\nConfidentiality is breached: An attacker may obtain files that should not be open to the public.\n\n### Credits\nSecurity researcher **Masashi Yamane of LAC Co., Ltd** reported this vulnerability to **JPCERT/CC Vulnerability Coordination Group** and they contacted us to coordinate a patch for the security issue.\n","aliases":["CVE-2023-29159","PYSEC-2023-83"],"modified":"2026-05-01T04:30:06.309717930Z","published":"2023-05-17T03:49:14Z","database_specific":{"severity":"MODERATE","github_reviewed":true,"github_reviewed_at":"2023-05-17T03:49:14Z","nvd_published_at":null,"cwe_ids":["CWE-22"]},"references":[{"type":"WEB","url":"https://github.com/encode/starlette/security/advisories/GHSA-v5gw-mw7f-84px"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2023-29159"},{"type":"WEB","url":"https://github.com/encode/starlette/commit/1797de464124b090f10cf570441e8292936d63e3"},{"type":"PACKAGE","url":"https://github.com/encode/starlette"},{"type":"WEB","url":"https://github.com/encode/starlette/blob/4bab981d9e870f6cee1bd4cd59b87ddaf355b2dc/starlette/staticfiles.py#L172-L174"},{"type":"WEB","url":"https://github.com/encode/starlette/releases/tag/0.27.0"},{"type":"WEB","url":"https://github.com/pypa/advisory-database/tree/main/vulns/starlette/PYSEC-2023-83.yaml"},{"type":"WEB","url":"https://jvn.jp/en/jp/JVN95981715"}],"affected":[{"package":{"name":"starlette","ecosystem":"PyPI","purl":"pkg:pypi/starlette"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.13.5"},{"fixed":"0.27.0"}]}],"versions":["0.13.5","0.13.6","0.13.7","0.13.8","0.14.0","0.14.1","0.14.2","0.15.0","0.16.0","0.17.0","0.17.1","0.18.0","0.19.0","0.19.1","0.20.0","0.20.1","0.20.2","0.20.3","0.20.4","0.21.0","0.22.0","0.23.0","0.23.1","0.24.0","0.25.0","0.26.0","0.26.0.post1","0.26.1"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2023/05/GHSA-v5gw-mw7f-84px/GHSA-v5gw-mw7f-84px.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N"},{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N"}]}