GHSA-5h86-8mv2-jq9f
MEDIUMaiohttp is vulnerable to directory traversal
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
aiohttpReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Summary
Improperly configuring static resource resolution in aiohttp when used as a web server can result in the unauthorized reading of arbitrary files on the system.
Details
When using aiohttp as a web server and configuring static routes, it is necessary to specify the root path for static files. Additionally, the option 'follow_symlinks' can be used to determine whether to follow symbolic links outside the static root directory. When 'follow_symlinks' is set to True, there is no validation to check if a given file path is within the root directory.This can lead to directory traversal vulnerabilities, resulting in unauthorized access to arbitrary files on the system, even when symlinks are not present.
i.e. An application is only vulnerable with setup code like:
app.router.add_routes([
web.static("/static", "static/", follow_symlinks=True), # Remove follow_symlinks to avoid the vulnerability
])
Impact
This is a directory traversal vulnerability with CWE ID 22. When using aiohttp as a web server and enabling static resource resolution with follow_symlinks set to True, it can lead to this vulnerability. This vulnerability has been present since the introduction of the follow_symlinks parameter.
Workaround
Even if upgrading to a patched version of aiohttp, we recommend following these steps regardless.
If using follow_symlinks=True outside of a restricted local development environment, disable the option immediately. This option is NOT needed to follow symlinks which point to a location within the static root directory, it is only intended to allow a symlink to break out of the static directory. Even with this CVE fixed, there is still a substantial risk of misconfiguration when using this option on a server that accepts requests from remote users.
Additionally, aiohttp has always recommended using a reverse proxy server (such as nginx) to handle static resources and not to use these static resources in aiohttp for production environments. Doing so also protects against this vulnerability, and is why we expect the number of affected users to be very low.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | aiohttp | ≥ 1.0.5&&< 3.9.2 | 3.9.2 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
aiohttp 3.9.1 - directory traversal PoC
by Beatriz Fresno Naumova · Feb 4, 2026
Frequently Asked Questions
Is GHSA-5h86-8mv2-jq9f in your stack?
O3 detects GHSA-5h86-8mv2-jq9f across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.