HIGH

CVE-2026-55833

Netty SPDY zlib header block continues decoded expansion after maxHeaderSize truncation

CVSS v3

7.5

HIGH

EPSS Score

0.7 %

exploit probability, as of 2026-10-17

CISA KEV

known exploited

Exploitation

—

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

io.netty:netty-codec-httpMavenfrom 4.1.0.Final · fixed in 4.1.136.Final

Vendor advisories

CVE-2026-55833 Red Hat Product Security474 products fixed · 34 known affected
netty: io.netty/netty-codec-http: Netty: Denial of Service via SPDY header decompression amplification
openshift-serverless-1/kn-ekb-dispatcher-rhel9 as a component of OpenShift Serverless · openshift-serverless-1/kn-ekb-receiver-rhel9 as a component of OpenShift Serverless · openshift-serverless-1/kn-eventing-integrations-aws-ddb-streams-source-rhel9 as a component of OpenShift Serverless
RHSA-2026:76637 Red Hat Product Security1 product fixed
Red Hat Security Advisory: Apicurio Registry (container images) release and security update [ 3.3.3 GA ]
RHSA-2026:70277 Red Hat Product Security1 product fixed
Red Hat Security Advisory: Red Hat JBoss Enterprise Application Platform 8.1.8 security update
RHSA-2026:70230 Red Hat Product Security147 products fixed
Red Hat Security Advisory: Red Hat JBoss Enterprise Application Platform 8.1.8 security update
RHSA-2026:70228 Red Hat Product Security148 products fixed
Red Hat Security Advisory: Red Hat JBoss Enterprise Application Platform 8.1.8 security update
RHSA-2026:70229 Red Hat Product Security148 products fixed
Red Hat Security Advisory: Red Hat JBoss Enterprise Application Platform 8.1.8 security update

11 more advisories

Full record on NVD

Description

Netty is a network application framework for development of protocol servers and clients. Prior to 4.1.136.Final and 4.2.16.Final, Netty SPDY header decoding continues inflating zlib-compressed header blocks after the raw header parser has exceeded `maxHeaderSize` and marked the frame truncated in `SpdyFrameCodec`, allowing a remote peer to send a small compressed `HEADERS` block that expands into much larger raw header data and causes compression-amplified CPU and allocation churn. This issue is fixed in versions 4.1.136.Final and 4.2.16.Final.

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published: 2026-07-21
Last Modified: 2026-07-21
GitHub Advisory: GHSA-mvh2-crg5-v77c

Frequently asked questions

What is CVE-2026-55833?

Is CVE-2026-55833 actively exploited?

Active exploitation of CVE-2026-55833 has not been confirmed. Its EPSS score was 0.7% on 2026-10-17, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-55833?

CVE-2026-55833 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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