What’s Vulnerable › Vulnerabilities

CVE-2021-21330: Open redirect vulnerability in aiohttp

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.9% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-02-26 · updated 2026-06-17
• Weakness: CWE-601

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.

Affected products

• aio-libs aiohttp: before 3.7.4 — fixed in 3.7.4
• Debian Linux: 10.0
• Fedoraproject Fedora: 33, 34

How to fix

Upgrade to a fixed version: aio-libs aiohttp 3.7.4. Check the vendor advisory for mitigations.

References

• https://github.com/aio-libs/aiohttp/blob/master/CHANGES.rst#374-2021-02-25
• https://github.com/aio-libs/aiohttp/commit/2545222a3853e31ace15d87ae0e2effb7da0c96b
• https://github.com/aio-libs/aiohttp/security/advisories/GHSA-v6wp-4m6f-gcjg
• 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/
• https://security.gentoo.org/glsa/202208-19
• https://www.debian.org/security/2021/dsa-4864
• https://github.com/aio-libs/aiohttp/blob/master/CHANGES.rst#374-2021-02-25
• https://github.com/aio-libs/aiohttp/commit/2545222a3853e31ace15d87ae0e2effb7da0c96b
• https://github.com/aio-libs/aiohttp/security/advisories/GHSA-v6wp-4m6f-gcjg
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FU7ENI54JNEK3PHEFGCE46DGMFNTVU6L/

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