vulntracker.iovulntracker.io
© 2026 vulntracker.io

CVE-2021-21409

Possible request smuggling in HTTP/2 due missing validation of content-length

MEDIUM
5.9
CVSS Score
Published: March 30, 2021 at 03:05 PM UTC
Updated: October 8, 2026 at 10:17 PM UTC
18 products affected across 5 vendorsDebian LinuxOnCommand Workflow AutomationJD Edwards EnterpriseOne Tools

Using netty by netty?

Get instant alerts when new vulnerabilities affect netty - before attackers find them.

Real-time alertsTrack your software stackFree plan available
Start FreeSign In
Severity
MEDIUM5.9
Exploit prediction
EPSS 5%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

References (59)

x_refsource_MISCThird Party Advisory
Source: [email protected]
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-21295
x_refsource_MISCPatchThird Party Advisory
Source: [email protected]
https://github.com/netty/netty/commit/b0fa4d5aab4215f3c22ce6123dd8dd5f38dc0432
x_refsource_CONFIRMThird Party Advisory
Source: [email protected]
https://github.com/netty/netty/security/advisories/GHSA-f256-j965-7f32
x_refsource_CONFIRMx_refsource_MISCThird Party Advisory
Source: [email protected]
https://github.com/netty/netty/security/advisories/GHSA-wm47-8v5p-wjpj
Mailing Listx_refsource_MLIST
Source: [email protected]
https://lists.apache.org/thread.html/r0b09f3e31e004fe583f677f7afa46bd30110904576c13c5ac818ac2c%40%3Cissues.flink.apache.org%3E
Mailing Listx_refsource_MLIST
Source: [email protected]
https://lists.apache.org/thread.html/r0ca82fec33334e571fe5b388272260778883e307e15415d7b1443de2%40%3Cissues.zookeeper.apache.org%3E
Mailing Listx_refsource_MLIST
Source: [email protected]
https://lists.apache.org/thread.html/r101f82d8f3b5af0bf79aecbd5b2dd3b404f6bb51d1a54c2c3d29bed9%40%3Cnotifications.zookeeper.apache.org%3E
Mailing Listx_refsource_MLIST
Source: [email protected]
https://lists.apache.org/thread.html/r1b3cb056364794f919aaf26ceaf7423de64e7fdd05a914066e7d5219%40%3Cissues.zookeeper.apache.org%3E

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.9MEDIUMGitHub_M
Attack Vector
NETWORK
Complexity
HIGH
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
HIGH
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-444

Get alerted

Stop reading CVE feeds looking for your own stack

Track the products you run and VulnTracker tells you when a new CVE affects them — with what is known about fixing it, and nothing about the rest.

Create accountSign in
Free plan, no card