HIGH

CVE-2026-56819

Netty: HTTP/2 decompression leaks ByteBuf reference count when the decompressor channel is already closed (Direct memory leak / OOM DoS)

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-http2Mavenfrom 4.1.0.Final · fixed in 4.1.136.Final

Vendor advisories

CVE-2026-56819 Red Hat Product Security30 products fixed · 35 known affected
io.netty/netty-codec-http2: Netty: Denial of Service via HTTP/2 DATA frame memory leak
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-2026:69296 Red Hat Product Security1 product fixed
Red Hat Security Advisory: Red Hat Data Grid 8.6.3 security update
RHSA-2026:68754 Red Hat Product Security4 products fixed
Red Hat Security Advisory: Red Hat OpenShift Dev Spaces 3.30.1 Release.
RHSA-2026:68333 Red Hat Product Security6 products fixed
Red Hat Security Advisory: Red Hat build of Cryostat security update
RHSA-2026:66488 Red Hat Product Security1 product fixed
Red Hat Security Advisory: Red Hat AMQ Broker 7.14.1 release and security update

7 more advisories

Full record on NVD

Description

Netty is a network application framework for development of protocol servers and clients. In versions 4.2.0.Final through 4.2.15.Final and 4.1.0.Final through 4.1.135.Final, a remote unauthenticated peer can leak one direct `ByteBuf` per HTTP/2 `DATA` frame in applications that enable HTTP/2 content decompression via `DelegatingDecompressorFrameListener`. When a `DATA` frame is processed for a stream whose decompressor has already been closed, `Http2Decompressor.decompress(...)` calls `decompressor.writeInbound(data.retain())` and does not release the retained buffer on the error path, eventually exhausting direct memory and crashing the JVM. 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: 2026-07-23

Frequently asked questions

What is CVE-2026-56819?

Is CVE-2026-56819 actively exploited?

Active exploitation of CVE-2026-56819 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-2026-56819?

CVE-2026-56819 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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