CVE-2021-21295Possible request smuggling in HTTP/2 due missing validation
Updated under an hour ago ()
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It affects netty io.netty:netty-codec-http2 and 8 other products. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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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`.
- CVSS
- 5.9 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
- Weakness (CWE)
- CWE-444
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- GitHub_M
- NVD analysis
- Modified
- Record last updated
- Oct 8, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
netty io.netty:netty-codec-http2 netty:io.netty_netty_codec_http2 (from the name) | before 4.1.60.Final | CNA record |
netty netty netty:netty | before 4.1.60 | NVD |
netapp oncommand_api_services netapp:oncommand_api_services | all versions | NVD |
netapp oncommand_workflow_automation netapp:oncommand_workflow_automation | all versions | NVD |
debian debian_linux debian:debian_linux | 10.0 | NVD |
quarkus quarkus quarkus:quarkus | through 1.13.7 | NVD |
apache kudu apache:kudu | before 1.16.0 | NVD |
apache zookeeper apache:zookeeper | 3.5.9 | NVD |
oracle communications_cloud_native_core_policy oracle:communications_cloud_native_core_policy | 1.14.0 | NVD |
References
- https://github.com/netty/netty/security/advisories/GHSA-wm47-8v5p-wjpjx-refsource-confirm
- https://github.com/Netflix/zuul/pull/980x-refsource-misc
- https://github.com/netty/netty/commit/89c241e3b1795ff257af4ad6eadc616cb2fb3dc4x-refsource-misc
- https://lists.apache.org/thread.html/r02e467123d45006a1dda20a38349e9c74c3a4b53e2e07be0939ecb3f%40%3Cdev.ranger.apache.org%3Emailing-list, x-refsource-mlist
- https://lists.apache.org/thread.html/r7bb3cdc192e9a6f863d3ea05422f09fa1ae2b88d4663e63696ee7ef5%40%3Cdev.ranger.apache.org%3Emailing-list, x-refsource-mlist
- https://lists.apache.org/thread.html/rcd163e421273e8dca1c71ea298dce3dd11b41d51c3a812e0394e6a5d%40%3Ccommits.pulsar.apache.org%3Emailing-list, x-refsource-mlist
- https://lists.apache.org/thread.html/r9924ef9357537722b28d04c98a189750b80694a19754e5057c34ca48%40%3Ccommits.pulsar.apache.org%3Emailing-list, x-refsource-mlist
- https://lists.apache.org/thread.html/rb51d6202ff1a773f96eaa694b7da4ad3f44922c40b3d4e1a19c2f325%40%3Ccommits.pulsar.apache.org%3Emailing-list, x-refsource-mlist
- https://lists.apache.org/thread.html/r790c2926efcd062067eb18fde2486527596d7275381cfaff2f7b3890%40%3Cissues.bookkeeper.apache.org%3Emailing-list, x-refsource-mlist
- https://lists.apache.org/thread.html/r1908a34b9cc7120e5c19968a116ddbcffea5e9deb76c2be4fa461904%40%3Cdev.zookeeper.apache.org%3Emailing-list, x-refsource-mlist
- https://lists.apache.org/thread.html/rb06c1e766aa45ee422e8261a8249b561784186483e8f742ea627bda4%40%3Cdev.kafka.apache.org%3Emailing-list, x-refsource-mlist
- https://lists.apache.org/thread.html/r5e66e286afb5506cdfe9bbf68a323e8d09614f6d1ddc806ed0224700%40%3Cjira.kafka.apache.org%3Emailing-list, x-refsource-mlist
- https://lists.apache.org/thread.html/rb592033a2462548d061a83ac9449c5ff66098751748fcd1e2d008233%40%3Cissues.zookeeper.apache.org%3Emailing-list, x-refsource-mlist
- https://lists.apache.org/thread.html/r59bac5c09f7a4179b9e2460e8f41c278aaf3b9a21cc23678eb893e41%40%3Cjira.kafka.apache.org%3Emailing-list, x-refsource-mlist
- https://lists.apache.org/thread.html/rc0087125cb15b4b78e44000f841cd37fefedfda942fd7ddf3ad1b528%40%3Cissues.zookeeper.apache.org%3Emailing-list, x-refsource-mlist
- https://lists.apache.org/thread.html/r1bca0b81193b74a451fc6d687ab58ef3a1f5ec40f6c61561d8dd9509%40%3Cissues.zookeeper.apache.org%3Emailing-list, x-refsource-mlist
- https://lists.apache.org/thread.html/r3ff9e735ca33612d900607dc139ebd38a64cadc6bce292e53eb86d7f%40%3Cissues.zookeeper.apache.org%3Emailing-list, x-refsource-mlist
- https://lists.apache.org/thread.html/r312ce5bd3c6bf08c138349b507b6f1c25fe9cf40b6f2b0014c9d12b1%40%3Cnotifications.zookeeper.apache.org%3Emailing-list, x-refsource-mlist
- https://lists.apache.org/thread.html/rcfc535afd413d9934d6ee509dce234dac41fa3747a7555befb17447e%40%3Cissues.zookeeper.apache.org%3Emailing-list, x-refsource-mlist
- https://lists.apache.org/thread.html/r3c293431c781696681abbfe1c573c2d9dcdae6fd3ff330ea22f0433f%40%3Cjira.kafka.apache.org%3Emailing-list, x-refsource-mlist
- https://lists.apache.org/thread.html/r9051e4f484a970b5566dc1870ecd9c1eb435214e2652cf3ea4d0c0cc%40%3Cjira.kafka.apache.org%3Emailing-list, x-refsource-mlist
- https://lists.apache.org/thread.html/rbadcbcb50195f00bbd196403865ced521ca70787999583c07be38d0e%40%3Cnotifications.zookeeper.apache.org%3Emailing-list, x-refsource-mlist
- https://lists.apache.org/thread.html/r67e6a636cbc1958383a1cd72b7fd0cd7493360b1dd0e6c12f5761798%40%3Cnotifications.zookeeper.apache.org%3Emailing-list, x-refsource-mlist
- https://lists.apache.org/thread.html/r6a29316d758db628a1df49ca219d64caf493999b52cc77847bfba675%40%3Cnotifications.zookeeper.apache.org%3Emailing-list, x-refsource-mlist
- https://lists.apache.org/thread.html/r5470456cf1409a99893ae9dd57439799f6dc1a60fda90e11570f66fe%40%3Cnotifications.zookeeper.apache.org%3Emailing-list, x-refsource-mlist
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.