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NVD / CVE Program· CNA GitHub_M

CVE-2021-43797: HTTP fails to validate against control chars in header names which may lead to HTTP request smuggling

Noroxi assessment

Priority: Monitor (action score 27/100)

  • 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: 2.8% (FIRST EPSS); higher than 86.9% 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: netty netty 4.1.71.Final.
  • Mentioned 4 times in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to netty netty 4.1.71.Final 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

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.

MediumCVSS 6.5 · v3.1—No exploit Fix available
Published
Dec 9, 2021
Updated
Oct 8, 2026
EPSS
2.8% · 86th percentile

Report tools

JSON

Action score

27

Monitor

Low priority for now.

CVSS
26 / 40 · 6.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 2.8%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
6.5
CNA · GitHub_M
6.5
agree

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-2021-43797

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
nettynetty
quarkusquarkus
netapponcommand workflow automation
netappsnapcenter
oraclebanking deposits and lines of credit servicing
oraclebanking party management
oraclebanking platform
oraclecoherence
oraclecommunications cloud native core binding support function
oraclecommunications cloud native core network slice selection function
oraclecommunications cloud native core policy
oraclecommunications cloud native core security edge protection proxy

and 6 more

Affected versions

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

  • debian debian linux10.0
  • debian debian linux11.0
  • netapp oncommand workflow automationall versions
  • netapp snapcenterall versions
  • netty nettybefore 4.1.71
  • oracle banking deposits and lines of credit servicing2.7
  • oracle banking party management2.7.0
  • oracle banking platform2.6.2
  • oracle coherence12.2.1.4.0
  • oracle coherence14.1.1.0.0
  • oracle communications cloud native core binding support function1.11.0
  • oracle communications cloud native core network slice selection function1.8.0
  • oracle communications cloud native core policy1.15.0
  • oracle communications cloud native core security edge protection proxy1.7.0
  • oracle communications cloud native core unified data repository1.15.0
  • oracle communications design studio7.4.2
  • oracle communications instant messaging server8.1
  • oracle helidon1.4.10
  • oracle helidon2.4.0
  • oracle peoplesoft enterprise peopletools8.58

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.

  • netty netty

    • <= 4.1.7.0.Finalaffected

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:10nettybefore 1:4.1.33-1+deb10u31:4.1.33-1+deb10u3
Debian:11nettybefore 1:4.1.48-4+deb11u11:4.1.48-4+deb11u1
Debian:12nettybefore 1:4.1.48-61:4.1.48-6
Mavenio.netty:nettyfrom 0—
Mavenio.netty:netty-codec-httpfrom 4.0.0 · before 4.1.71.Final4.1.71.Final
Mavenorg.jboss.netty:nettyfrom 0—
openSUSE:Leap 15.3nettybefore 4.1.75-150200.4.6.24.1.75-150200.4.6.2
openSUSE:Leap 15.3netty3before 3.10.6-150200.3.3.23.10.6-150200.3.3.2
openSUSE:Tumbleweednettybefore 4.1.72-1.14.1.72-1.1
openSUSE:Tumbleweednetty3before 3.10.6-9.13.10.6-9.1
Red Hat:jboss_enterprise_application_platform:7.4::el7eap7-activemq-artemisbefore 0:2.16.0-9.redhat_00042.1.el7eap0:2.16.0-9.redhat_00042.1.el7eap
Red Hat:jboss_enterprise_application_platform:7.4::el7eap7-activemq-artemis-clibefore 0:2.16.0-9.redhat_00042.1.el7eap0:2.16.0-9.redhat_00042.1.el7eap
Red Hat:jboss_enterprise_application_platform:7.4::el7eap7-activemq-artemis-commonsbefore 0:2.16.0-9.redhat_00042.1.el7eap0:2.16.0-9.redhat_00042.1.el7eap
Red Hat:jboss_enterprise_application_platform:7.4::el7eap7-activemq-artemis-core-clientbefore 0:2.16.0-9.redhat_00042.1.el7eap0:2.16.0-9.redhat_00042.1.el7eap
Red Hat:jboss_enterprise_application_platform:7.4::el7eap7-activemq-artemis-dtobefore 0:2.16.0-9.redhat_00042.1.el7eap0:2.16.0-9.redhat_00042.1.el7eap
Red Hat:jboss_enterprise_application_platform:7.4::el7eap7-activemq-artemis-hornetq-protocolbefore 0:2.16.0-9.redhat_00042.1.el7eap0:2.16.0-9.redhat_00042.1.el7eap
Red Hat:jboss_enterprise_application_platform:7.4::el7eap7-activemq-artemis-hqclient-protocolbefore 0:2.16.0-9.redhat_00042.1.el7eap0:2.16.0-9.redhat_00042.1.el7eap
Red Hat:jboss_enterprise_application_platform:7.4::el7eap7-activemq-artemis-jdbc-storebefore 0:2.16.0-9.redhat_00042.1.el7eap0:2.16.0-9.redhat_00042.1.el7eap
Red Hat:jboss_enterprise_application_platform:7.4::el7eap7-activemq-artemis-jms-clientbefore 0:2.16.0-9.redhat_00042.1.el7eap0:2.16.0-9.redhat_00042.1.el7eap
Red Hat:jboss_enterprise_application_platform:7.4::el7eap7-activemq-artemis-jms-serverbefore 0:2.16.0-9.redhat_00042.1.el7eap0:2.16.0-9.redhat_00042.1.el7eap
Red Hat:jboss_enterprise_application_platform:7.4::el7eap7-activemq-artemis-journalbefore 0:2.16.0-9.redhat_00042.1.el7eap0:2.16.0-9.redhat_00042.1.el7eap
Red Hat:jboss_enterprise_application_platform:7.4::el7eap7-activemq-artemis-rabefore 0:2.16.0-9.redhat_00042.1.el7eap0:2.16.0-9.redhat_00042.1.el7eap
Red Hat:jboss_enterprise_application_platform:7.4::el7eap7-activemq-artemis-selectorbefore 0:2.16.0-9.redhat_00042.1.el7eap0:2.16.0-9.redhat_00042.1.el7eap
Red Hat:jboss_enterprise_application_platform:7.4::el7eap7-activemq-artemis-serverbefore 0:2.16.0-9.redhat_00042.1.el7eap0:2.16.0-9.redhat_00042.1.el7eap

+96

Same product

netty: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-47691Netty has Insufficient Bailiwick Validation for NS Records
    40Plan
  • CVE-2026-45674Netty Vulnerable to DNS Cache Poisoning via Missing Bailiwick Checks in CNAME Records
    40Plan
  • CVE-2019-20445HttpObjectDecoder.java in Netty before 4.1.44 allows a Content-Length header to be accompanied by a second Content-Length header, or by a Tr
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2021-37136Oct 19, 2021 · The Bzip2 decompression decoder function doesn't allow setting size restrictions on the decompressed output data (which affects the allocati
    32Monitor
  • ← EarlierCVE-2021-37137Oct 19, 2021 · The Snappy frame decoder function doesn't restrict the chunk length which may lead to excessive memory usage.
    32Monitor
  • Later →CVE-2022-24823May 6, 2022 · Local Information Disclosure Vulnerability in io.netty:netty-codec-http
    22Monitor

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
netty netty4.1.71.Final · descriptionVendor (CNA)
debian:netty1:4.1.48-6 · Debian:12Package registry (OSV)
Maven:io.netty:netty-codec-http4.1.71.FinalPackage registry (OSV)
opensuse:netty4.1.75-150200.4.6.2 · openSUSE:Leap 15.3Package registry (OSV)
opensuse:netty33.10.6-150200.3.3.2 · openSUSE:Leap 15.3Package registry (OSV)
red hat:eap7-jackson-databind0:2.12.6.1-1.redhat_00003.1.el7eap · Red Hat:jboss_enterprise_application_platform:7.4::el7Package registry (OSV)
red hat:eap7-netty0:4.1.72-4.Final_redhat_00001.1.el7eap · Red Hat:jboss_enterprise_application_platform:7.4::el7Package registry (OSV)
red hat:eap7-netty-all0:4.1.72-4.Final_redhat_00001.1.el7eap · Red Hat:jboss_enterprise_application_platform:7.4::el7Package registry (OSV)
red hat:eap7-netty-buffer0:4.1.72-4.Final_redhat_00001.1.el7eap · Red Hat:jboss_enterprise_application_platform:7.4::el7Package registry (OSV)
red hat:eap7-netty-codec0:4.1.72-4.Final_redhat_00001.1.el7eap · Red Hat:jboss_enterprise_application_platform:7.4::el7Package registry (OSV)
red hat:eap7-netty-codec-dns0:4.1.72-4.Final_redhat_00001.1.el7eap · Red Hat:jboss_enterprise_application_platform:7.4::el7Package registry (OSV)
red hat:eap7-netty-codec-haproxy0:4.1.72-4.Final_redhat_00001.1.el7eap · Red Hat:jboss_enterprise_application_platform:7.4::el7Package registry (OSV)
red hat:eap7-netty-codec-http0:4.1.72-4.Final_redhat_00001.1.el7eap · Red Hat:jboss_enterprise_application_platform:7.4::el7Package registry (OSV)
red hat:eap7-netty-codec-http20:4.1.72-4.Final_redhat_00001.1.el7eap · Red Hat:jboss_enterprise_application_platform:7.4::el7Package registry (OSV)
red hat:eap7-netty-codec-memcache0:4.1.72-4.Final_redhat_00001.1.el7eap · Red Hat:jboss_enterprise_application_platform:7.4::el7Package registry (OSV)
red hat:eap7-netty-codec-mqtt0:4.1.72-4.Final_redhat_00001.1.el7eap · Red Hat:jboss_enterprise_application_platform:7.4::el7Package registry (OSV)
red hat:eap7-netty-codec-redis0:4.1.72-4.Final_redhat_00001.1.el7eap · Red Hat:jboss_enterprise_application_platform:7.4::el7Package registry (OSV)
rocky linux:libdb0:5.3.28-42.el8_4 · Rocky Linux:8Package registry (OSV)
suse:netty33.10.6-150200.3.3.2 · SUSE:Linux Enterprise Module for Development Tools 15 SP3Package 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.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

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

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

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
none
Integrity
high · data or configuration can be modified
Availability
none
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality impact
None
Integrity impact
High
Availability impact
None

Weakness class (CWE)

CWE-444 · Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

CVSS vector

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

—

Change log

  1. SSVC exploitation— → none
  2. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (6 more)

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

All records