WaratekVRT Sign in

CVE-2021-21295 Netty

Affected softwareNetty
Severity5.9 Medium CVSS 3.1 3 scores
Fixed in4.1.60.Final
WeaknessCWE-444
Published9 Mar 2021
Updated8 Oct 2026

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 4.1.60.Final there is a vulnerability that enables request smuggling. If a Content-Length header is present in the original HTTP/2 request, the field is not validated by Http2MultiplexHandler as it is propagated up. This is fine as long as the request is not proxied through as HTTP/1.1. If the request comes in as an HTTP/2 stream, gets converted into the HTTP/1.1 domain objects (HttpRequest, HttpContent, etc.) via Http2StreamFrameToHttpObjectCodec and then sent up to the child channel's pipeline and proxied through a remote peer as HTTP/1.1 this may result in request smuggling. In a proxy case, users may assume the content-length is validated somehow, which is not the case. If the request is forwarded to a backend channel that is a HTTP/1.1 connection, the Content-Length now has meaning and needs to be checked. An attacker can smuggle requests inside the body as it gets downgraded from HTTP/2 to HTTP/1.1. For an example attack refer to the linked GitHub Advisory. Users are only affected if all of this is true: HTTP2MultiplexCodec or Http2FrameCodec is used, Http2StreamFrameToHttpObjectCodec is used to convert to HTTP/1.1 objects, and these HTTP/1.1 objects are forwarded to another remote peer. This has been patched in 4.1.60.Final As a workaround, the user can do the validation by themselves by implementing a custom ChannelInboundHandler that is put in the ChannelPipeline behind Http2StreamFrameToHttpObjectCodec.

Exploitation status

No public exploit

No exploit has been reported in the sources we check. Published 5 years ago.

  • CISA KEV not listed
  • VulnCheck KEV not listed
  • CISA Vulnrichment exploitation: none
  • Indexed PoC none indexed
  • EPSS 19% chance in 30 days A model's forecast, not a report of exploitation. Higher than 97% of all scored CVEs.

Waratek protection

No exploit published

Within Waratek scope. In the sources we check, nobody has published exploit code for this CVE or reported it being exploited.

A public code fix exists: netty/netty 89c241e.

  • Protection none
  • Action unverified
  • Review automated Upstream data
  • Record active
Decided by Exploit code for this candidate, published in a reviewed catalogue or a GitHub repository with 5 or more stars, or in use per CISA or VulnCheck; not only a CISA verdict, a forecast, or nothing at all
Finding This CVE is not listed in CISA KEV or VulnCheck KEV, CISA Vulnrichment records no active exploitation, no reviewed exploit catalogue carries an entry for it, and no GitHub PoC repository for it has 5 or more stars. Nobody has published exploit code worth tracing, so it is not a candidate for a rule ahead of the ones where somebody has; an upstream fix path does exist, so the remediation half of the candidacy still holds. This is a statement about what has been published, not about whether the defect is reachable or serious.
Candidate fix https://github.com/netty/netty/commit/89c241e3b1795ff257af4ad6eadc616cb2fb3dc4 : a commit: the change itself

CVSS

5.9 MEDIUM v3.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N 3 metrics

We show the highest score from the newest CVSS version. Scores from different versions can't be compared, and the first score listed is sometimes a 0.0 placeholder.

VersionScoreBandVectorAssignerType
CVSS 3.1 5.9 MEDIUM CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N security-advisories@github.com Secondary published
CVSS 3.1 5.9 MEDIUM CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N NVD Primary
CVSS 2.0 2.6 none AV:N/AC:H/Au:N/C:N/I:P/A:N NVD Primary

Affected software and releases

Oracle advisories

AdvisoryTypeQuarterProducts Oracle names in its risk matrix
Oracle Critical Patch Update July 2023 ↗ CPU 2023-Q3 Oracle Siebel CRM / Siebel Core (Apache ZooKeeper) (23.5 and prior)
Oracle Critical Patch Update October 2022 ↗ CPU 2022-Q4 Oracle Communications Applications / REST Service Manager (Netty) (12.0.0.4.0-12.0.0.6.0)

Oracle components and versions

FamilyComponentVersions, as Oracle lists themRead as
Oracle Communications Applications REST Service Manager (Netty) 12.0.0.4.0-12.0.0.6.0
Oracle Siebel CRM Siebel Core (Apache ZooKeeper) 23.5 and prior

Maven packages

Affected and fixed versions, from OSV.dev
PackageIntroducedFixedLast affected
io.netty:netty-codec-http2 4.0.0 4.1.60.Final unbounded
org.jboss.netty:netty 0 none unbounded
io.netty:netty 0 none unbounded

Products and versions

11 products, 11 version entries
SourceVendorProductSchemeAffected versions
nvd apache kudu generic < 1.16.0
nvd apache zookeeper generic 3.5.9
nvd debian debian linux generic 10.0
osv io.netty netty generic any version
osv io.netty netty-codec-http2 generic ≥ 4.0.0 and < 4.1.60
nvd netapp oncommand api services generic any version
nvd netapp oncommand workflow automation generic any version
nvd netty netty generic < 4.1.60
nvd oracle communications cloud native core policy generic 1.14.0
osv org.jboss.netty netty generic any version
nvd quarkus quarkus generic ≤ 1.13.7

References

URLTags
https://github.com/netty/netty/commit/89c241e3b1795ff257af4ad6eadc616cb2fb3dc4 commit
https://github.com/netty/netty/security/advisories/GHSA-wm47-8v5p-wjpj WEB
https://github.com/Netflix/zuul/pull/980 WEB
https://lists.apache.org/thread.html/rc73b8dd01b1be276d06bdf07883ecd93fe1a01f139a99ef30ba4308c@%3Ccommits.servicecomb.apache.org%3E WEB
https://lists.apache.org/thread.html/rc165e36ca7cb5417aec3f21bbc4ec00fb38ecebdd96a82cfab9bd56f@%3Cjira.kafka.apache.org%3E WEB
https://lists.apache.org/thread.html/rc0087125cb15b4b78e44000f841cd37fefedfda942fd7ddf3ad1b528@%3Cissues.zookeeper.apache.org%3E WEB
https://lists.apache.org/thread.html/rbed09768f496244a2e138dbbe6d2847ddf796c9c8ef9e50f2e3e30d9@%3Cnotifications.zookeeper.apache.org%3E WEB
https://lists.apache.org/thread.html/rbadcbcb50195f00bbd196403865ced521ca70787999583c07be38d0e@%3Cnotifications.zookeeper.apache.org%3E WEB
https://lists.apache.org/thread.html/rb95d42ce220ed4a4683aa17833b5006d657bc4254bc5cb03cd5e6bfb@%3Cissues.hbase.apache.org%3E WEB
https://lists.apache.org/thread.html/rb592033a2462548d061a83ac9449c5ff66098751748fcd1e2d008233@%3Cissues.zookeeper.apache.org%3E WEB

Timeline

Published2021-03-09By the CVE Program.
NVD record modified2026-10-08NVD's own last-modified date for this record.