Critical severity · published May 13, 2026
CVE-2026-42584
Netty: HttpClientCodec response desynchronization
9.1
CVSS
0.8%
EPSS
No
On KEV
Description
Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, HttpClientCodec pairs each inbound response with an outbound request by queue.poll() once per response, including for 1xx. If the client pipelines GET then HEAD and the server sends 103, then 200 with GET body, then 200 for HEAD, the queue pairs HEAD with the first 200. The HEAD rule then skips reading that message’s body, so the GET entity bytes stay on the stream and the following 200 is parsed from the wrong offset. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.8% · higher than 58% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
NE
netty · netty
>= 4.2.0.Alpha1, < 4.2.13.Final; < 4.1.133.Final · source: vendor, NVD
NE
netty-codec-http · io.netty
>= 4.2.0.Alpha1, < 4.2.13.Final; < 4.1.133.Final · source: vendor
C4
Cryostat 4 on RHEL 9 · Red Hat
All versions, or not specified · source: CISA
OS
OpenShift Serverless · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat AMQ Broker 7.13.6 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat AMQ Broker 7.14.1 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat AMQ Clients · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Build of Keycloak · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Data Grid 8 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux AI (RHEL AI) 3 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Fuse 7 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 7 · Red Hat
All versions, or not specified · source: CISA
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-42584
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-42584
Exploit
https://github.com/netty/netty/security/advisories/GHSA-57rv-r2g8-2cj3
access.redhat.com
https://access.redhat.com/errata/RHSA-2026:23808
access.redhat.com
https://access.redhat.com/errata/RHSA-2026:24502
access.redhat.com
https://access.redhat.com/errata/RHSA-2026:25123
access.redhat.com
https://access.redhat.com/errata/RHSA-2026:28010
access.redhat.com
https://access.redhat.com/errata/RHSA-2026:36820
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