CVE-2025-69224: AIOHTTP Header Parsing Vulnerability Leading to Request Smuggling
Summary
CVE-2025-69224: AIOHTTP's unicode processing of header values could cause parsing discrepancies. Affects aiohttp versions < 3.13.3. Fixed in 3.13.3. How to fix ↓
Also tracked for
The same CVE-2025-69224 is tracked separately for each ecosystem and vendor. Its fix information is the same; the package and affected versions differ.
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Background
AIOHTTP is a popular Python library used for building asynchronous web applications. It provides an easy-to-use interface for handling HTTP requests and responses, making it a preferred choice for developers working with asynchronous programming in Python. However, AIOHTTP's handling of header values, particularly those containing non-ASCII characters, has exposed it to potential request smuggling attacks, especially when used without C extensions.
Vulnerability Detail
The vulnerability arises from the Python HTTP parser's inability to correctly process non-ASCII characters in header values. This flaw can be exploited by attackers to perform request smuggling attacks, allowing them to bypass firewalls or proxy protections. If a pure Python version of AIOHTTP is in use, or if AIOHTTP_NO_EXTENSIONS is enabled, the risk of such attacks increases significantly. The vulnerability is classified under CWE-444, which pertains to 'Inconsistent Interpretation of HTTP Requests ('Request Smuggling').'
How To Fix
Latest published version: 3.14.5 as of 22 Oct 2026
pip install --upgrade "aiohttp==3.14.5"Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
3.13.3
This is the first release that contains the fix.
pip install --upgrade "aiohttp==3.13.3"Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
If immediate upgrading is not feasible, consider disabling the use of non-ASCII characters in header values as a temporary workaround. This can help mitigate the risk of request smuggling attacks until the library is updated.
Conclusion
The AIOHTTP vulnerability identified as CVE-2025-69224 poses a significant risk due to its potential for request smuggling attacks. It is crucial for developers using AIOHTTP to update to the latest version to mitigate this risk. Additionally, utilizing tools like Vulert can help in monitoring and managing vulnerabilities effectively.
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FAQ
Request smuggling is a technique used by attackers to send multiple HTTP requests in a single connection, which can lead to unexpected behavior in web applications and allow them to bypass security measures.
You can use the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without requiring any signup.
If exploited, this vulnerability can allow attackers to bypass firewalls and proxy protections, potentially leading to unauthorized access or data breaches.
Yes, updating to AIOHTTP version 3.13.3 or later will ensure that you are using a version that has addressed this vulnerability.
Vulert is a tool that monitors and alerts in real-time for open-source vulnerabilities in software. It uses the Pipfile.lock to track vulnerabilities, making it easier for developers to maintain secure applications.
References
Related vulnerabilities
Recent vulnerabilities recorded for aiohttp.
