No exploitation reportedFix available

CVE-2021-43797

No exploitation reported by the sources we read.

Published2021-12-09
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 asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients. Netty prior to version 4.1.71.Final skips control chars when they are present at the beginning / end of the header name. It should instead fail fast as these are not allowed by the spec and could lead to HTTP request smuggling. Failing to do the validation might cause netty to "sanitize" header names before it forward these to another remote system when used as proxy. This remote system can't see the invalid usage anymore, and therefore does not do the validation itself. Users should upgrade to version 4.1.71.Final.

Timeline

dates in UTC

2021-12-0919:15CVE 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-2021-43797?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-43797?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Debian debian linux

Branch	Affected	Fixed in	Source
10.0	= 10.0	no fix published	NVD
11.0	= 11.0	no fix published	NVD

Oracle coherence

Branch	Affected	Fixed in	Source
12.2	= 12.2.1.4.0	no fix published	NVD
14.1	= 14.1.1.0.0	no fix published	NVD

Oracle helidon

Branch	Affected	Fixed in	Source
1.4	= 1.4.10	no fix published	NVD
2.4	= 2.4.0	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.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Vendor advisories

RHSA-2022:2217 Red Hat Product Security3 products fixed
Red Hat Security Advisory: Red Hat OpenShift Logging Security and Bug update Release 5.3.7
RHSA-2022:2218 Red Hat Product Security3 products fixed
Red Hat Security Advisory: Openshift Logging Security and Bug update Release (5.2.10)
RHSA-2022:2216 Red Hat Product Security4 products fixed
Red Hat Security Advisory: Red Hat OpenShift Logging Security and Bug update Release 5.4.1

Full record on NVD

Fix

Vendor fix Red Hat Product Security RHSA-2022:2217 · 3 productsFor OpenShift Container Platform 4.10 see the following documentation, which will be updated shortly for this release, for important instructions on how to upgrade your cluster and fully apply this errata update: https://docs.openshift.com/container-platform/4.10/release_notes/ocp-4-10-release-not…
Vendor fix Red Hat Product Security RHSA-2022:2218 · 3 productsFor OpenShift Container Platform 4.8 see the following documentation, which will be updated shortly for this release, for important instructions on how to upgrade your cluster and fully apply this errata update: https://docs.openshift.com/container-platform/4.8/release_notes/ocp-4-8-release-notes.…
Vendor fix Red Hat Product Security RHSA-2022:2216 · 4 productsFor OpenShift Container Platform 4.9 see the following documentation, which will be updated shortly for this release, for important instructions on how to upgrade your cluster and fully apply this errata update: https://docs.openshift.com/container-platform/4.9/release_notes/ocp-4-9-release-notes.…

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 3.16.5read 2026-10-23
NVDCVSS 3.16.5read 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 score2.9 %2026-10-23
OSVaffected packages—

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
Published: 2021-12-09
Last Modified: 2026-10-08
NVD status: Modified

Frequently asked questions

What is CVE-2021-43797?

Is CVE-2021-43797 actively exploited?

Active exploitation of CVE-2021-43797 has not been confirmed. Its EPSS score was 2.9% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-43797?

CVE-2021-43797 has a CVSS v3 base score of 6.5 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N.

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