CVE-2021-21330

mediumpriority · track · 25EPSS 0.019 · 80 %ileEURUUS
grimoire priorityP3 · Track
Exploitable?
—
no known exploitation
Likely / severe?
1.91% (80th) EPSS
CVSS 5.8 · medium
Is it mine?
13 products
Check your exposure
Who says so?
5 sources
cnnvd · enisa_euvd · fstec_bdu · osv

EPSS · scored 2026-10-27

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.

01

cvss

Technical severity, 0–10. One row per scoring source.

6.1
010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · low–medium · 3.1–6.1

v2.05.8mediumAV:N/AC:M/Au:N/C:P/I:P/A:Nprimary · NVD / NIST USexploitability 8.6 · impact 4.9
v3.16.1mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:Nprimary · NVD / NIST USexploitability 2.8 · impact 2.7
v3.14.7mediumAV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:Nsecondary · FSTEC (BDU) RU
v3.13.1lowCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:Nsecondary · ENISA EU
v3.13.1lowCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:Nsecondary · security-advisories@github.comexploitability 1.6 · impact 1.4
v3.13.1lowCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:Nsecondary · OSV
v3.15.6mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N/E:Usecondary · CVSS-BT (t0sche)
02

weaknesses

The CWE weakness classes this flaw belongs to.

03

affected products (13)

Products and version ranges known to be affected.

04

advisories (2)

Vendor and ecosystem advisories describing this.

  • GHSA-v6wp-4m6f-gcjg`aiohttp` Open Redirect vulnerability (`normalize_path_middleware` middleware)2021-02-26ghsa · osvUS

    ### 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

  • PYSEC-2021-762021-02-26vendor · osvUS

    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.

05

also known as (7)

Other names and identifiers for this entity.

06

sources

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published 2021-02-26modified 2026-06-17
08

references (32)

External citations — patches, advisories, analysis.

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