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CVE-2026-56819

Netty denial of service

7.5 HIGHPublic exploitEPSS 0.66%
  1. Published21 Jul 2026

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

Netty≥ 4.1.0 < 4.1.136 · ≥ 4.2.0 < 4.2.16

Remediation

Fixed in
Netty≥ 4.1.136

References

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Frequently asked

Is CVE-2026-56819 being actively exploited?

CVE-2026-56819 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.66%.

How severe is CVE-2026-56819?

CVE-2026-56819 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.66% probability of exploitation.

Which products are affected by CVE-2026-56819?

Affected products include Netty.

How do I fix CVE-2026-56819?

Upgrade affected software to a fixed version, for example Netty 4.1.136 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-56819 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.