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CVE-2026-56816

Netty denial of service

7.5 HIGHPublic exploitEPSS 0.64%
  1. Published21 Jul 2026

Description

Netty is a network application framework for development of protocol servers and clients. Prior to 4.2.16.Final, Netty's `Http3FrameCodec` buffers incoming data for HTTP/3 reserved frame types up to the wire-specified payload length without limits; `decodeFrame` trusts `payLoadLength`, allowing an attacker to open multiple QUIC streams and send reserved frames with very large payload lengths to cause memory exhaustion and denial of service. This issue is fixed in version 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≥ 4.2.2 < 4.2.16

Remediation

Fixed in
Netty≥ 4.2.16

References

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Frequently asked

Is CVE-2026-56816 being actively exploited?

CVE-2026-56816 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.64%.

How severe is CVE-2026-56816?

CVE-2026-56816 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.64% probability of exploitation.

Which products are affected by CVE-2026-56816?

Affected products include Netty.

How do I fix CVE-2026-56816?

Upgrade affected software to a fixed version, for example Netty 4.2.16 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-56816 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.