No exploitation reportedFix available

CVE-2021-21409

No exploitation reported by the sources we read.

Published2021-03-30
WeaknessCWE-444

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

Netty is an open-source, asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients. In Netty (io.netty:netty-codec-http2) before version 4.1.61.Final there is a vulnerability that enables request smuggling. The content-length header is not correctly validated if the request only uses a single Http2HeaderFrame with the endStream set to to true. This could lead to request smuggling if the request is proxied to a remote peer and translated to HTTP/1.1. This is a followup of GHSA-wm47-8v5p-wjpj/CVE-2021-21295 which did miss to fix this one case. This was fixed as part of 4.1.61.Final.

Timeline

dates in UTC

2021-03-3015:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-21409?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-21409?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Oracle banking corporate lending process management

Branch	Affected	Fixed in	Source
14.2	= 14.2.0	no fix published	NVD
14.3	= 14.3.0	no fix published	NVD
14.5	= 14.5.0	no fix published	NVD

Oracle banking credit facilities process management

Branch	Affected	Fixed in	Source
14.2	= 14.2.0	no fix published	NVD
14.3	= 14.3.0	no fix published	NVD
14.5	= 14.5.0	no fix published	NVD

Oracle banking trade finance process management

Branch	Affected	Fixed in	Source
14.2	= 14.2.0	no fix published	NVD
14.3	= 14.3.0	no fix published	NVD
14.5	= 14.5.0	no fix published	NVD

18 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Advisories and patches

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

CISA-ADPSSVC decisionnone2026-10-08
OpenCVESSVC decisionnone—
CNACVSS 3.15.9read 2026-10-23
NVDCVSS 3.15.9read 2026-10-23
NVDCVSS 2.04.3read 2026-10-23
CNAweakness (CWE)CWE-444read 2026-10-23
NVDweakness (CWE)CWE-444read 2026-10-23
FIRST EPSSEPSS score4.9 %2026-10-23
OSVaffected packages—

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
Published: 2021-03-30
Last Modified: 2026-10-08
NVD status: Modified

Frequently asked questions

What is CVE-2021-21409?

Is CVE-2021-21409 actively exploited?

Active exploitation of CVE-2021-21409 has not been confirmed. Its EPSS score was 4.9% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-21409?

CVE-2021-21409 has a CVSS v3 base score of 5.9 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N.

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