HOMEVULNERABILITIESCVE-2021-21409
MEDIUM

CVE-2021-21409

CWE-444Published: March 30, 2021· Updated: Jun 17, 2026

5.9
CVSS v3.1

Official 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.

NVD Source

Technical Analysis

CVE-2021-21409 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in full integrity compromise (data manipulation), with a CVSS base score of 5.9.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityHigh
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityNone
IntegrityHigh
AvailabilityNone
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

Affected Vendors & Products

Debian1 product(s)
debian linux
netapp2 product(s)
oncommand api servicesoncommand workflow automation
netty1 product(s)
netty
Oracle13 product(s)
banking corporate lending process managementbanking credit facilities process managementbanking trade finance process managementcoherencecommunications brm - elastic charging enginecommunications cloud native core consolecommunications cloud native core policycommunications design studiocommunications messaging serverhelidonjd edwards enterpriseone toolsnosql database+1
quarkus1 product(s)
quarkus
Source: NVD CPE · 26 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

PATCHhttps://github.com/netty/netty/commit/b0fa4d5aab4215f3c22ce6123dd8dd5f38dc0432
PATCHhttps://www.oracle.com//security-alerts/cpujul2021.html
PATCHhttps://www.oracle.com/security-alerts/cpuapr2022.html
PATCHhttps://www.oracle.com/security-alerts/cpujan2022.html
PATCHhttps://www.oracle.com/security-alerts/cpuoct2021.html
PATCHhttps://github.com/netty/netty/commit/b0fa4d5aab4215f3c22ce6123dd8dd5f38dc0432
PATCHhttps://www.oracle.com//security-alerts/cpujul2021.html
PATCHhttps://www.oracle.com/security-alerts/cpuapr2022.html
PATCHhttps://www.oracle.com/security-alerts/cpujan2022.html
PATCHhttps://www.oracle.com/security-alerts/cpuoct2021.html
ADVISORYhttps://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-21295
ADVISORYhttps://github.com/netty/netty/security/advisories/GHSA-f256-j965-7f32
ADVISORYhttps://github.com/netty/netty/security/advisories/GHSA-wm47-8v5p-wjpj
ADVISORYhttps://security.netapp.com/advisory/ntap-20210604-0003/
ADVISORYhttps://www.debian.org/security/2021/dsa-4885
ADVISORYhttps://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-21295
ADVISORYhttps://github.com/netty/netty/security/advisories/GHSA-f256-j965-7f32
ADVISORYhttps://github.com/netty/netty/security/advisories/GHSA-wm47-8v5p-wjpj
ADVISORYhttps://security.netapp.com/advisory/ntap-20210604-0003/
ADVISORYhttps://www.debian.org/security/2021/dsa-4885

All References (118)

→
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-21295Third Party Advisory
→
https://github.com/netty/netty/commit/b0fa4d5aab4215f3c22ce6123dd8dd5f38dc0432Patch · Third Party Advisory
→
https://github.com/netty/netty/security/advisories/GHSA-f256-j965-7f32Third Party Advisory
→
https://github.com/netty/netty/security/advisories/GHSA-wm47-8v5p-wjpjThird Party Advisory
→
https://lists.apache.org/thread.html/r0b09f3e31e004fe583f677f7afa46bd30110904576c13c5ac818ac2c%40%3Cissues.flink.apache.org%3E
→
https://lists.apache.org/thread.html/r0ca82fec33334e571fe5b388272260778883e307e15415d7b1443de2%40%3Cissues.zookeeper.apache.org%3E
→
https://lists.apache.org/thread.html/r101f82d8f3b5af0bf79aecbd5b2dd3b404f6bb51d1a54c2c3d29bed9%40%3Cnotifications.zookeeper.apache.org%3E
→
https://lists.apache.org/thread.html/r1b3cb056364794f919aaf26ceaf7423de64e7fdd05a914066e7d5219%40%3Cissues.zookeeper.apache.org%3E
→
https://lists.apache.org/thread.html/r2732aa3884cacfecac4c54cfaa77c279ba815cad44b464a567216f83%40%3Cissues.zookeeper.apache.org%3E
→
https://lists.apache.org/thread.html/r31044fb995e894749cb821c6fe56f487c16a97028e6e360e59f09d58%40%3Cissues.zookeeper.apache.org%3E
→
https://lists.apache.org/thread.html/r4a98827bb4a7edbd69ef862f2351391845697c40711820d10df52ca5%40%3Ccommits.zookeeper.apache.org%3E
→
https://lists.apache.org/thread.html/r4b8be87acf5b9c098a2ee350b5ca5716fe7afeaf0a21a4ee45a90687%40%3Cissues.zookeeper.apache.org%3E
→
https://lists.apache.org/thread.html/r4ea2f1a9d79d4fc1896e085f31fb60a21b1770d0a26a5250f849372d%40%3Cissues.kudu.apache.org%3E
→
https://lists.apache.org/thread.html/r584cf871f188c406d8bd447ff4e2fd9817fca862436c064d0951a071%40%3Ccommits.pulsar.apache.org%3E
→
https://lists.apache.org/thread.html/r5baac01f9e06c40ff7aab209d5751b3b58802c63734e33324b70a06a%40%3Cissues.flink.apache.org%3E

Quick Facts

CVE IDCVE-2021-21409
CVSS Score5.9 / 10
SeverityMEDIUM
WeaknessCWE-444
CISA KEVNo
Affected5 vendor(s)
PublishedMar 30, 2021

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CVE-2016-10711
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CVE-2019-15605
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Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-21409 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWatch. CVE data is provided under the NVD usage policy.
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