CVE-2021-21330

Name: CVE-2021-21330
Creator: NVD / NIST
Published: 2021-02-26T03:15:12.84+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.1/10EPSS 1.91%

Last modified Jun 17, 2026

CVE-2021-21330 is a medium-severity vulnerability rated 6.1/10 on the CVSS scale. aiohttp is an asynchronous HTTP client/server framework for asyncio and Python. In aiohttp before version 3.7.4 there is an open redirect vulnerability. EPSS estimates a 1.91% chance of exploitation in the next 30 days.

Description

aiohttp is an asynchronous HTTP client/server framework for asyncio and Python. In aiohttp before version 3.7.4 there is an open redirect vulnerability. A maliciously crafted link to an aiohttp-based web-server could redirect the browser to a different website. It is caused by a bug in the `aiohttp.web_middlewares.normalize_path_middleware` middleware. This security problem has been fixed in 3.7.4. Upgrade your dependency using pip as follows "pip install aiohttp >= 3.7.4". If upgrading is not an option for you, a workaround can be to avoid using `aiohttp.web_middlewares.normalize_path_middleware` in your applications.

Metrics

CVSS 3.1

6.1/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS Probability

1.91%

77.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Aiohttp	Aiohttp	< 3.7.4
Debian	Debian Linux	10.0
Fedoraproject	Fedora	33
Fedoraproject	Fedora	34

References

https://github.com/aio-libs/aiohttp/blob/master/CHANGES.rst#374-2021-02-25Third Party Advisory
https://github.com/aio-libs/aiohttp/commit/2545222a3853e31ace15d87ae0e2effb7da0c96bPatch, Third Party Advisory
https://github.com/aio-libs/aiohttp/security/advisories/GHSA-v6wp-4m6f-gcjgThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FU7ENI54JNEK3PHEFGCE46DGMFNTVU6L/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JN3V7CZJRT4QFCVXB6LDPCJH7NAOFCA5/
https://pypi.org/project/aiohttp/Product, Third Party Advisory
https://security.gentoo.org/glsa/202208-19Third Party Advisory
https://www.debian.org/security/2021/dsa-4864Third Party Advisory
https://github.com/aio-libs/aiohttp/blob/master/CHANGES.rst#374-2021-02-25Third Party Advisory
https://github.com/aio-libs/aiohttp/commit/2545222a3853e31ace15d87ae0e2effb7da0c96bPatch, Third Party Advisory
https://github.com/aio-libs/aiohttp/security/advisories/GHSA-v6wp-4m6f-gcjgThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FU7ENI54JNEK3PHEFGCE46DGMFNTVU6L/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JN3V7CZJRT4QFCVXB6LDPCJH7NAOFCA5/
https://pypi.org/project/aiohttp/Product, Third Party Advisory
https://security.gentoo.org/glsa/202208-19Third Party Advisory
https://www.debian.org/security/2021/dsa-4864Third Party Advisory

Timeline

Published: Feb 26, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-21330?

How severe is CVE-2021-21330?

CVE-2021-21330 has a CVSS score of 6.1/10 (MEDIUM severity). The EPSS model estimates a 1.91% probability of exploitation in the next 30 days.

How do I fix CVE-2021-21330?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-21330?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST