Possible request smuggling in HTTP/2 due missing validation
Impact
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. A sample attack request looks like:
POST / HTTP/2
:authority:: externaldomain.com
Content-Length: 4
asdfGET /evilRedirect HTTP/1.1
Host: internaldomain.comUsers are only affected if all of this is true:
HTTP2MultiplexCodecorHttp2FrameCodecis usedHttp2StreamFrameToHttpObjectCodecis used to convert to HTTP/1.1 objects- These HTTP/1.1 objects are forwarded to another remote peer.
Patches
This has been patched in 4.1.60.Final
Workarounds
The user can do the validation by themselves by implementing a custom ChannelInboundHandler that is put in the ChannelPipeline behind Http2StreamFrameToHttpObjectCodec.
References
Related change to workaround the problem: https://github.com/Netflix/zuul/pull/980
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Java / Kotlin (Maven) | io.netty:netty | all versions | no fix |
| Java / Kotlin (Maven) | io.netty:netty-codec-http2 | >= 4.0.0, < 4.1.60.Final | 4.1.60.Final |
| Java / Kotlin (Maven) | org.jboss.netty:netty | all versions | no fix |
References
- https://github.com/netty/netty/security/advisories/GHSA-wm47-8v5p-wjpj
- https://nvd.nist.gov/vuln/detail/CVE-2021-21295
- https://github.com/Netflix/zuul/pull/980
- https://github.com/netty/netty/commit/89c241e3b1795ff257af4ad6eadc616cb2fb3dc4
- https://lists.apache.org/thread.html/rc73b8dd01b1be276d06bdf07883ecd93fe1a01f139a99ef30ba4308c@%3Ccommits.servicecomb.apache.org%3E
- https://lists.apache.org/thread.html/rc165e36ca7cb5417aec3f21bbc4ec00fb38ecebdd96a82cfab9bd56f@%3Cjira.kafka.apache.org%3E
- https://lists.apache.org/thread.html/rc0087125cb15b4b78e44000f841cd37fefedfda942fd7ddf3ad1b528@%3Cissues.zookeeper.apache.org%3E
- https://lists.apache.org/thread.html/rbed09768f496244a2e138dbbe6d2847ddf796c9c8ef9e50f2e3e30d9@%3Cnotifications.zookeeper.apache.org%3E
- https://lists.apache.org/thread.html/rbadcbcb50195f00bbd196403865ced521ca70787999583c07be38d0e@%3Cnotifications.zookeeper.apache.org%3E
- https://lists.apache.org/thread.html/rb95d42ce220ed4a4683aa17833b5006d657bc4254bc5cb03cd5e6bfb@%3Cissues.hbase.apache.org%3E
- https://lists.apache.org/thread.html/rb592033a2462548d061a83ac9449c5ff66098751748fcd1e2d008233@%3Cissues.zookeeper.apache.org%3E
- https://lists.apache.org/thread.html/rb523bb6c60196c5f58514b86a8585c2069a4852039b45de3818b29d2@%3Ccommits.servicecomb.apache.org%3E
- https://lists.apache.org/thread.html/rb51d6202ff1a773f96eaa694b7da4ad3f44922c40b3d4e1a19c2f325@%3Ccommits.pulsar.apache.org%3E
- https://lists.apache.org/thread.html/rb06c1e766aa45ee422e8261a8249b561784186483e8f742ea627bda4@%3Cdev.kafka.apache.org%3E
- https://lists.apache.org/thread.html/rae198f44c3f7ac5264045e6ba976be1703cff38dcf1609916e50210d@%3Ccommits.servicecomb.apache.org%3E
- https://lists.apache.org/thread.html/racc191a1f70a4f13155e8002c61bddef2870b26441971c697436ad5d@%3Ccommits.servicecomb.apache.org%3E
- https://lists.apache.org/thread.html/ra96c74c37ed7252f78392e1ad16442bd16ae72a4d6c8db50dd55c88b@%3Ccommits.servicecomb.apache.org%3E
- https://lists.apache.org/thread.html/ra83096bcbfe6e1f4d54449f8a013117a0536404e9d307ab4a0d34f81@%3Cissues.hbase.apache.org%3E
- https://lists.apache.org/thread.html/ra655e5cec74d1ddf62adacb71d398abd96f3ea2c588f6bbf048348eb@%3Cissues.kudu.apache.org%3E
- https://lists.apache.org/thread.html/ra64d56a8a331ffd7bdcd24a9aaaeeedeacd5d639f5a683389123f898@%3Cdev.flink.apache.org%3E
- https://lists.apache.org/thread.html/r9924ef9357537722b28d04c98a189750b80694a19754e5057c34ca48@%3Ccommits.pulsar.apache.org%3E
- https://lists.apache.org/thread.html/r96ce18044880c33634c4b3fcecc57b8b90673c9364d63eba00385523@%3Cjira.kafka.apache.org%3E
- https://lists.apache.org/thread.html/r905b92099998291956eebf4f1c5d95f5a0cbcece2946cc46d32274fd@%3Cdev.hbase.apache.org%3E
- https://lists.apache.org/thread.html/r9051e4f484a970b5566dc1870ecd9c1eb435214e2652cf3ea4d0c0cc@%3Cjira.kafka.apache.org%3E
- https://lists.apache.org/thread.html/r8db1d7b3b9acc9e8d2776395e280eb9615dd7790e1da8c57039963de@%3Cnotifications.zookeeper.apache.org%3E
- https://lists.apache.org/thread.html/r8bcaf7821247b1836b10f6a1a3a3212b06272fd4cde4a859de1b78cf@%3Ccommits.servicecomb.apache.org%3E
- https://www.oracle.com/security-alerts/cpuapr2022.html
- https://www.debian.org/security/2021/dsa-4885
- https://security.netapp.com/advisory/ntap-20210604-0003
- https://lists.apache.org/thread.html/rfff6ff8ffb31e8a32619c79774def44b6ffbb037c128c5ad3eab7171@%3Cissues.zookeeper.apache.org%3E
- https://lists.apache.org/thread.html/rf934292a4a1c189827f625d567838d2c1001e4739b158638d844105b@%3Cissues.kudu.apache.org%3E
- https://lists.apache.org/thread.html/rf87b870a22aa5c77c27900967b518a71a7d954c2952860fce3794b60@%3Ccommits.servicecomb.apache.org%3E
- https://lists.apache.org/thread.html/rf36f1114e84a3379b20587063686148e2d5a39abc0b8a66ff2a9087a@%3Cissues.zookeeper.apache.org%3E
- https://lists.apache.org/thread.html/reafc834062486adfc7be5bb8f7b7793be0d33f483678a094c3f9d468@%3Ccommits.servicecomb.apache.org%3E
- https://lists.apache.org/thread.html/re7c69756a102bebce8b8681882844a53e2f23975a189363e68ad0324@%3Cissues.flink.apache.org%3E
- https://lists.apache.org/thread.html/re6207ebe2ca4d44f2a6deee695ad6f27fd29d78980f1d46ed1574f91@%3Cissues.zookeeper.apache.org%3E
- https://lists.apache.org/thread.html/re4f70b62843e92163fab03b65e2aa8078693293a0c36f1cc260079ed@%3Ccommits.servicecomb.apache.org%3E
- https://lists.apache.org/thread.html/rddbb4f8d5db23265bb63d14ef4b3723b438abc1589f877db11d35450@%3Cissues.zookeeper.apache.org%3E
- https://lists.apache.org/thread.html/rdc096e13ac4501ea2e2b03a197682a313b85d3d3ec89d5ae5551b384@%3Cissues.zookeeper.apache.org%3E
- https://lists.apache.org/thread.html/rdb4db3f5a9c478ca52a7b164680b88877a5a9c174e7047676c006b2c@%3Ccommits.servicecomb.apache.org%3E
- CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N- Weakness (CWE)
CWE-444- Platform
- Java / Kotlin (Maven)
- Package
io.netty:netty, io.netty:netty-codec-http2, org.jboss.netty:netty- Disclosed
- 09.03.2021
- Updated
- 11.10.2026 13:19
Sources and licenses
OSV / GitHub Advisory Database - GHSA-wm47-8v5p-wjpj - CC BY 4.0
Vulnerability history: io.netty:netty
All published vulnerabilities of this package (Java / Kotlin (Maven)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 11
- First → latest
- 10.2019 05.2022
- Without a fix
- 9
- Exploited in attacks
- 0
Severity breakdown
- Critical 1
- High 4
- Medium 6
Disclosures per year
- 2019: 1
- 2020: 3
- 2021: 6
- 2022: 1
- 2023: 0
- 2024: 0
- 2025: 0
- 2026: 0
-
Possible request smuggling in HTTP/2 due missing validation this entry
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