CVE-2026-56816Public exploitNetwork attack vector

Service interruption via unchecked HTTP/3 frame length

Published Jul 21, 2026 · Updated Jul 21, 2026

Uncontrolled resource consumption in Netty before 4.2.16.Final allows remote attackers to exhaust memory through reserved HTTP/3 frames. Http3FrameCodec.decodeFrame trusts the wire-supplied payLoadLength and retains stream data until that unchecked reserved-frame length is reached. Only applications using Netty's HTTP/3 codec are exposed; concurrent QUIC streams can force an out-of-memory condition and interrupt service.

CVSS severity7.5
High
EPSS probability0.52%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uncontrolled resource consumption in Netty before 4.2.16.Final allows remote attackers to exhaust memory through reserved HTTP/3 frames. Http3FrameCodec.decodeFrame trusts the wire-supplied payLoadLength and retains stream data until that unchecked reserved-frame length is reached. Only applications using Netty's HTTP/3 codec are exposed; concurrent QUIC streams can force an out-of-memory condition and interrupt service.

The record

CVE
CVE-2026-56816
Published
Jul 21, 2026
Updated
Jul 21, 2026
Vendor
The Netty Project
Product
Netty
Classifications
CWE-400, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 21, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 4.2.16.Final

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Netty Project · Nettyversion=< 4.2.16.Final

Published CVSS scores

7.5GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499Endpoint Denial of Service

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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