GHSA-v5gw-mw7f-84px
LOWStarlette has Path Traversal vulnerability in StaticFiles
EPSS Exploitation Probability
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Blast Radius
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Description
Summary
When 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.
Details
The root cause of this issue is the usage of os.path.commonprefix():
https://github.com/encode/starlette/blob/4bab981d9e870f6cee1bd4cd59b87ddaf355b2dc/starlette/staticfiles.py#L172-L174
As 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.
When 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.
The 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.
PoC
In order to reproduce the issue, you need to create the following structure:
├── static
│ ├── index.html
├── static_disallow
│ ├── index.html
└── static1.txt
And run the Starlette app with:
import uvicorn
from starlette.applications import Starlette
from starlette.routing import Mount
from starlette.staticfiles import StaticFiles
routes = [
Mount("/static", app=StaticFiles(directory="static", html=True), name="static"),
]
app = Starlette(routes=routes)
if __name__ == "__main__":
uvicorn.run(app, host="0.0.0.0", port=8000)
And running the commands:
curl --path-as-is 'localhost:8000/static/../static_disallow/'
curl --path-as-is 'localhost:8000/static/../static1.txt'
The static1.txt and the directory static_disallow are exposed.
Impact
Confidentiality is breached: An attacker may obtain files that should not be open to the public.
Credits
Security 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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | starlette | ≥ 0.13.5&&< 0.27.0 | 0.27.0 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for starlette. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update starlette to 0.27.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-v5gw-mw7f-84px is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-v5gw-mw7f-84px is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-v5gw-mw7f-84px. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-v5gw-mw7f-84px in your dependencies?
O3 detects GHSA-v5gw-mw7f-84px across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.