CVE-2024-23334: aiohttp.web.static(follow_symlinks=True) is vulnerable to directory traversal
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 'followsymlinks' can be used to determine whether to follow symbolic links outside the static root directory. When 'followsymlinks' 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.addroutes([ web.static("/static", "static/", followsymlinks=True), # Remove followsymlinks 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 followsymlinks set to True, it can lead to this vulnerability. This vulnerability has been present since the introduction of the followsymlinks parameter.
Workaround Even if upgrading to a patched version of aiohttp, we recommend following these steps regardless.
If using followsymlinks=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.
-----
Patch: https://github.com/aio-libs/aiohttp/pull/8079/files
Other sources
aiohttp is an asynchronous HTTP client/server framework for asyncio and Python. 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 'followsymlinks' can be used to determine whether to follow symbolic links outside the static root directory. When 'followsymlinks' is set to True, there is no validation to check if reading a file 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. Disabling followsymlinks and using a reverse proxy are encouraged mitigations. Version 3.9.2 fixes this issue.
— Debian
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
pip/aiohttpto a version that resolves this vulnerability.Fixed in 3.9.2 - Upgrade
Upgrade
debian/python-aiohttpto a version that resolves this vulnerability.Fixed in 3.10.5-1 - Upgrade
Upgrade
redhat/aiohttpto a version that resolves this vulnerability.Fixed in 3.9.2 - Upgrade
Upgrade
aio-libs/aiohttpto a version that resolves this vulnerability.Fixed in 3.9.2Patch aiohttp/pull/8079 - Configuration
Disable symlink following for static file routing; e.g., remove `follow_symlinks=True` from `web.static('/static', 'static/', follow_symlinks=True)` (set to False).
aiohttp.web.static follow_symlinks = False - Compensating control
Use a reverse proxy (such as nginx) to handle static resources instead of serving static resources directly from aiohttp in production environments.
Event History
Frequently Asked Questions
What is the severity of CVE-2024-23334?
CVE-2024-23334 is considered a high-severity vulnerability due to the potential for unauthorized file access.
How do I fix CVE-2024-23334?
To fix CVE-2024-23334, update aiohttp to version 3.9.2 or later.
What systems are affected by CVE-2024-23334?
CVE-2024-23334 affects aiohttp versions between 1.0.5 and 3.9.2 when used as a web server.
What happens if I don't address CVE-2024-23334?
Failure to address CVE-2024-23334 could lead to unauthorized reading of sensitive files on the system.
Is CVE-2024-23334 related to static file configuration?
Yes, CVE-2024-23334 is specifically related to improperly configuring static resource resolution in aiohttp.