CVE-2023-49081

Improper validation make it possible for an attacker to modify the HTTP request (e.g. to insert a new header) or even create a new HTTP request if the attacker controls the HTTP version.

Details

The vulnerability only occurs if the attacker can control the HTTP version of the request (including its type).
For example if an unvalidated JSON value is used as a version and the attacker is then able to pass an array as the version parameter.
Furthermore, the vulnerability only occurs when the Connection header is passed to the headers parameter.

At this point, the library will use the parsed value to create the request. If a list is passed, then it bypasses validation and it is possible to perform CRLF injection.

PoC

The POC below shows an example of providing an unvalidated array as a version:
https://gist.github.com/jnovikov/184afb593d9c2114d77f508e0ccd508e

Workaround

If these specific conditions are met and you are unable to upgrade, then validate the user input to the version parameter to ensure it is a str.

Patch: https://github.com/aio-libs/aiohttp/pull/7835/files

CRLF injection leading to Request Smuggling.

The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.

CVE-2023-49081 has a CVSS score of 7.2 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.9.0); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2023-49081? CVE-2023-49081 is a medium-severity improper input validation vulnerability in aiohttp (pip), affecting versions < 3.9.0. It is fixed in 3.9.0. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
2. How severe is CVE-2023-49081? CVE-2023-49081 has a CVSS score of 7.2 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of aiohttp are affected by CVE-2023-49081? aiohttp (pip) versions < 3.9.0 is affected.
4. Is there a fix for CVE-2023-49081? Yes. CVE-2023-49081 is fixed in 3.9.0. Upgrade to this version or later.
5. Is CVE-2023-49081 exploitable, and should I be worried? Whether CVE-2023-49081 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2023-49081 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2023-49081? Upgrade aiohttp to 3.9.0 or later.

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