---
id: CVE-2021-21330
aliases:
  - GHSA-v6wp-4m6f-gcjg
  - PYSEC-2021-76
title: '`aiohttp` Open Redirect vulnerability (`normalize_path_middleware` middleware)'
summary: '`aiohttp` Open Redirect vulnerability (`normalize_path_middleware` middleware)'
severity: low
cvss: 3.1
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N'
vendor: aiohttp
product: aiohttp
ecosystem: pip
affected:
  - aiohttp < 3.7.4
patched:
  - aiohttp 3.7.4
published: '2021-02-26'
updated: '2026-07-08'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-v6wp-4m6f-gcjg'
references:
  - url: >-
      https://github.com/aio-libs/aiohttp/security/advisories/GHSA-v6wp-4m6f-gcjg
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2021-21330'
  - url: >-
      https://github.com/aio-libs/aiohttp/commit/2545222a3853e31ace15d87ae0e2effb7da0c96b
  - url: 'https://github.com/aio-libs/aiohttp'
  - url: 'https://github.com/aio-libs/aiohttp/blob/master/CHANGES.rst#374-2021-02-25'
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/aiohttp/PYSEC-2021-76.yaml
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FU7ENI54JNEK3PHEFGCE46DGMFNTVU6L
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JN3V7CZJRT4QFCVXB6LDPCJH7NAOFCA5
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/FU7ENI54JNEK3PHEFGCE46DGMFNTVU6L
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/JN3V7CZJRT4QFCVXB6LDPCJH7NAOFCA5
  - url: 'https://pypi.org/project/aiohttp'
  - url: 'https://security.gentoo.org/glsa/202208-19'
  - url: 'https://www.debian.org/security/2021/dsa-4864'
tags:
  - osv
  - pip
epss: 0.01905
epssPercentile: 0.78854
ingestedAt: '2026-07-08T18:25:53.109Z'
---

## Overview

### Impact

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.

### Patches

This security problem has been fixed in v3.7.4. Upgrade your dependency as follows:
[`pip install aiohttp >= 3.7.4`]

### Workarounds

If upgrading is not an option for you, a workaround can be to avoid using `aiohttp.web_middlewares.normalize_path_middleware` in your applications.

### References

* [aiohttp @ PyPI]
* [GHSA-v6wp-4m6f-gcjg]
* [OWASP page on open redirects]

### For more information

If you have any questions or comments about this advisory:
* Open an issue in the [aiohttp repo](https://github.com/aio-libs/aiohttp/issues/new/choose)
* Email us at wk+aio-libs-security@sydorenko.org.ua and/or andrew.svetlov+aio-libs-security@gmail.com

Credit: [Jelmer Vernooij] and [Beast Glatisant].

[aiohttp @ PyPI]: https://pypi.org/p/aiohttp
[`pip install aiohttp >= 3.7.4`]: https://pypi.org/project/aiohttp/3.7.4/
[GHSA-v6wp-4m6f-gcjg]: https://github.com/aio-libs/aiohttp/security/advisories/GHSA-v6wp-4m6f-gcjg
[OWASP page on open redirects]:
https://cheatsheetseries.owasp.org/cheatsheets/Unvalidated_Redirects_and_Forwards_Cheat_Sheet.html

[Jelmer Vernooij]: https://jelmer.uk
[Beast Glatisant]: https://github.com/g147

## Affected packages

- `aiohttp < 3.7.4`

## Remediation

Upgrade to a patched release:

- `aiohttp 3.7.4`