CVE-2021-21330

LOWNVD 3.13.1—
EchelonGraph scoreMEDIUM confidence

This low-severity CVE scores 3.1 under NVD CVSS v3. EPSS exploit probability: 1.9%, top 22% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Trending — 3 sources updated this week
3.1
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 2%CVSS: 3.1Exploit: NoneExposed: 0

A fix is available — apply it.

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.

CVSS v3
3.1
EG Score
3.1(medium)
EG Risk
—
EPSS
77.5%
KEV
Not listed

Published

February 26, 2021

Last Modified

November 21, 2024

References (16)

Vendor Advisories for CVE-2021-21330(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(2)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntupython3-aiohttp (3.6.2-1ubuntu0.1~esm1) @ focal2026-05-26ubuntu
redhatpython-aiohttp-0:3.7.4-1.el7pc2021-11-16redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFixed inDependents
aiohttp0.1 ... 3.7.3 (210 versions)3.7.4—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Additional Vendor Advisories

(1)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 10× in last 7d / 48× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 102 total refreshes for this CVE.

  1. 2026-07-22 22:43 UTCEG score recompute
  2. 2026-07-22 14:05 UTCEPSS rescore
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Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2021-21330?
CVE-2021-21330 is a low vulnerability published on February 26, 2021. 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…
When was CVE-2021-21330 disclosed?
CVE-2021-21330 was first published in the National Vulnerability Database on February 26, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-21330 actively exploited?
CVE-2021-21330 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 77.5% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-21330?
CVE-2021-21330 has a CVSS v3 base score of 3.1 (NVD).
How do I remediate CVE-2021-21330?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-21330, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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