What’s Vulnerable › Vulnerabilities

CVE-2021-21409: Possible request smuggling in HTTP/2 due missing validation of content-length

• Severity: medium (CVSS 5.9 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 4.9% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-03-30 · updated 2026-10-08
• Weakness: CWE-444

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 products

• Debian Linux: 10.0
• NetApp Oncommand Api Services: all versions
• NetApp OnCommand Workflow Automation: all versions
• netty: before 4.1.61 — fixed in 4.1.61
• Oracle Banking Corporate Lending Process Management: 14.2.0, 14.3.0, 14.5.0
• Oracle Banking Credit Facilities Process Management: 14.2.0, 14.3.0, 14.5.0
• Oracle Corporation Oracle Banking Trade Finance Process Management: 14.2.0, 14.3.0, 14.5.0
• Oracle Corporation Oracle Coherence: 12.2.1.4.0, 14.1.1.0.0
• Oracle Corporation Communications BRM - Elastic Charging Engine: 12.0.0.3
• Oracle Communications Cloud Native Core Console: 1.7.0
• Oracle Communications Cloud Native Core Policy: 1.14.0
• Oracle Communications Design Studio: 7.4.2.0.0
• Oracle Communications Messaging Server: 8.1
• Oracle Corporation Helidon: 1.4.10, 2.4.0
• Oracle Corporation JD Edwards EnterpriseOne Tools: before 9.2.6.3 — fixed in 9.2.6.3
• Oracle Nosql Database: before 21.1.12 — fixed in 21.1.12
• Oracle Corporation Primavera Gateway: from 17.12.0 through 17.12.11; from 18.8.0 through 18.8.11; from 19.12.0 through 19.12.10
• quarkusio quarkus: through 1.13.7

How to fix

Upgrade to a fixed version: netty 4.1.61; Oracle Corporation JD Edwards EnterpriseOne Tools 9.2.6.3; Oracle Nosql Database 21.1.12. Check the vendor advisory for mitigations.

References

• https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-21295
• https://github.com/netty/netty/commit/b0fa4d5aab4215f3c22ce6123dd8dd5f38dc0432
• https://github.com/netty/netty/security/advisories/GHSA-f256-j965-7f32
• https://github.com/netty/netty/security/advisories/GHSA-wm47-8v5p-wjpj
• 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

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