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NVD / CVE Program· CNA GitHub_M

CVE-2021-21330: Open redirect vulnerability in aiohttp

MediumCVSS 6.1 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 25/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 1.9% (FIRST EPSS); higher than 79.9% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. A user must open a link or visit a page. No special conditions are required; it is repeatable.
  • Fixed version: aio-libs aiohttp 3.7.4.
  • Severity is disputed: the assigning authority (CNA) scores it 3.1, NVD 6.1.

Low priority for now. Upgrade to aio-libs aiohttp 3.7.4 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

Published
Feb 25, 2021
Updated
Jun 16, 2026
EPSS
1.9% · 79th percentile

Report tools

JSON

Action score

25

Monitor

Low priority for now.

CVSS
24 / 40 · 6.1 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 1.9%

CNA vs NVD score

NVD
6.1
CNA · GitHub_M
3.1
3.0 point gap

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2021-21330

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
aiohttpaiohttp
debiandebian linux
fedoraprojectfedora

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • aio-libs aiohttp

    • < 3.7.4affected
Affected versions · NVD (4)

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • aiohttp aiohttpbefore 3.7.4
  • debian debian linux10.0
  • fedoraproject fedora33
  • fedoraproject fedora34

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:10python-aiohttpbefore 3.5.1-1+deb10u13.5.1-1+deb10u1
Debian:12python-aiohttpbefore 3.7.4-13.7.4-1
openSUSE:Leap 15.3python-aiohttpbefore 3.6.0-150100.3.9.13.6.0-150100.3.9.1
openSUSE:Leap 15.4python-typing_extensionsbefore 3.10.0.0-150400.3.2.13.10.0.0-150400.3.2.1
openSUSE:Tumbleweedpython-aiohttpbefore 3.14.3-1.13.14.3-1.1
openSUSE:Tumbleweedpython-aiohttpbefore 3.8.5-2.13.8.5-2.1
PyPIaiohttpbefore 3.7.43.7.4
Red Hat:satellite_capsule:6.10::el7foremanbefore 0:2.5.2.17-2.el7sat0:2.5.2.17-2.el7sat
Red Hat:satellite_capsule:6.10::el7python-aiohttpbefore 0:3.7.4-1.el7pc0:3.7.4-1.el7pc
Red Hat:satellite_capsule:6.10::el7python-ecdsabefore 0:0.13.3-2.el7pc0:0.13.3-2.el7pc
Red Hat:satellite_capsule:6.10::el7python-pyyamlbefore 0:5.4.1-1.el7pc0:5.4.1-1.el7pc
Red Hat:satellite_capsule:6.10::el7python-urllib3before 0:1.26.5-1.el7pc0:1.26.5-1.el7pc
Red Hat:satellite_capsule:6.10::el7python3-djangobefore 0:2.2.24-1.el7pc0:2.2.24-1.el7pc
Red Hat:satellite_capsule:6.10::el7python3-ecdsabefore 0:0.13.3-2.el7pc0:0.13.3-2.el7pc
Red Hat:satellite_capsule:6.10::el7python3-pyyamlbefore 0:5.4.1-1.el7pc0:5.4.1-1.el7pc
Red Hat:satellite_capsule:6.10::el7python3-urllib3before 0:1.26.5-1.el7pc0:1.26.5-1.el7pc
Red Hat:satellite_capsule:6.10::el7satellitebefore 0:6.10.0-3.el7sat0:6.10.0-3.el7sat
Red Hat:satellite_capsule:6.10::el7satellite-capsulebefore 0:6.10.0-3.el7sat0:6.10.0-3.el7sat
Red Hat:satellite_capsule:6.10::el7tfm-rubygem-nokogiribefore 0:1.11.3-2.el7sat0:1.11.3-2.el7sat
Red Hat:satellite:6.10::el7candlepinbefore 0:4.0.9-1.el7sat0:4.0.9-1.el7sat
Red Hat:satellite:6.10::el7tfm-rubygem-actionpackbefore 0:6.0.3.7-1.el7sat0:6.0.3.7-1.el7sat
Red Hat:satellite:6.10::el7tfm-rubygem-activerecord-session_storebefore 0:2.0.0-1.el7sat0:2.0.0-1.el7sat
Red Hat:satellite:6.10::el7tfm-rubygem-addressablebefore 0:2.8.0-1.el7sat0:2.8.0-1.el7sat
Red Hat:satellite:6.10::el7tfm-rubygem-pumabefore 0:5.3.2-1.el7sat0:5.3.2-1.el7sat

+5

Same product

aiohttp: all records

Other highest-scoring records for the same primary product.

  • CVE-2024-23334aiohttp.web.static(follow_symlinks=True) is vulnerable to directory traversal
    53Plan
  • CVE-2024-52303aiohttp memory leak when middleware is enabled when requesting a resource with a non-allowed method
    34Monitor
  • CVE-2025-69223AIOHTTP's HTTP Parser auto_decompress feature is vulnerable to zip bomb
    30Monitor

Published before and after this one in the same product

  • Later →CVE-2022-33124Jun 23, 2022 · AIOHTTP 3.8.1 can report a "ValueError: Invalid IPv6 URL" outcome, which can lead to a Denial of Service (DoS).
    22Monitor
  • Later →CVE-2023-37276Jul 19, 2023 · aiohttp vulnerable to HTTP request smuggling
    30Monitor
  • Later →CVE-2023-47627Nov 14, 2023 · Request smuggling in aiohttp
    30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
aio-libs aiohttp3.7.4 · descriptionVendor (CNA)
debian:python-aiohttp3.7.4-1 · Debian:12Package registry (OSV)
opensuse:python-aiohttp3.6.0-150100.3.9.1 · openSUSE:Leap 15.3Package registry (OSV)
opensuse:python-typing_extensions3.10.0.0-150400.3.2.1 · openSUSE:Leap 15.4Package registry (OSV)
PyPI:aiohttp3.7.4Package registry (OSV)
red hat:candlepin0:4.0.9-1.el7sat · Red Hat:satellite:6.10::el7Package registry (OSV)
red hat:foreman0:2.5.2.17-2.el7sat · Red Hat:satellite_capsule:6.10::el7Package registry (OSV)
red hat:python-aiohttp0:3.7.4-1.el7pc · Red Hat:satellite_capsule:6.10::el7Package registry (OSV)
red hat:python-ecdsa0:0.13.3-2.el7pc · Red Hat:satellite_capsule:6.10::el7Package registry (OSV)
red hat:python-pyyaml0:5.4.1-1.el7pc · Red Hat:satellite_capsule:6.10::el7Package registry (OSV)
red hat:python3-ecdsa0:0.13.3-2.el7pc · Red Hat:satellite_capsule:6.10::el7Package registry (OSV)
red hat:python3-pyyaml0:5.4.1-1.el7pc · Red Hat:satellite_capsule:6.10::el7Package registry (OSV)
red hat:satellite0:6.10.0-3.el7sat · Red Hat:satellite_capsule:6.10::el7Package registry (OSV)
red hat:satellite-capsule0:6.10.0-3.el7sat · Red Hat:satellite_capsule:6.10::el7Package registry (OSV)
red hat:tfm-rubygem-actionpack0:6.0.3.7-1.el7sat · Red Hat:satellite:6.10::el7Package registry (OSV)
red hat:tfm-rubygem-activerecord-session_store0:2.0.0-1.el7sat · Red Hat:satellite:6.10::el7Package registry (OSV)
red hat:tfm-rubygem-nokogiri0:1.11.3-2.el7sat · Red Hat:satellite_capsule:6.10::el7Package registry (OSV)
suse:python-aiohttp3.6.0-150100.3.9.1 · SUSE:Linux Enterprise Module for Public Cloud 15 SP1Package registry (OSV)
suse:python-typing_extensions3.10.0.0-150100.3.3.1 · SUSE:Linux Enterprise Module for Public Cloud 15 SP1Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Not on record for this CVE: EPSS history · researcher credit · variant or chain candidate · public bounty program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • A user must open a link or visit a page.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
low · data can be read
Integrity
low · data or configuration can be modified
Availability
none

Impact can extend beyond the vulnerable component (scope changes).

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Changed
Confidentiality impact
Low
Integrity impact
Low
Availability impact
None

Weakness class (CWE)

CWE-601 · URL Redirection to Untrusted Site ('Open Redirect')

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

References

Show all references (7 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records