CVE-2026-55831Public exploitNetwork attack vector

Service interruption via unbounded SPDY settings map

Published Jul 20, 2026 · Updated Jul 20, 2026

Resource exhaustion in Netty allows remote attackers to interrupt vulnerable SPDY/3.1 services with a crafted SETTINGS frame. SpdyFrameCodec accepts the peer-declared entry count without a cap and inserts each unique 24-bit ID into DefaultSpdySettingsFrame's TreeMap. Exploitation requires unauthenticated network access to a pipeline that enables SPDY/3.1; one valid frame can add 262144 entries and consume about 17–18 MiB of heap plus insertion CPU.

CVSS severity7.5
High
EPSS probability0.44%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Netty allows remote attackers to interrupt vulnerable SPDY/3.1 services with a crafted SETTINGS frame. SpdyFrameCodec accepts the peer-declared entry count without a cap and inserts each unique 24-bit ID into DefaultSpdySettingsFrame's TreeMap. Exploitation requires unauthenticated network access to a pipeline that enables SPDY/3.1; one valid frame can add 262144 entries and consume about 17–18 MiB of heap plus insertion CPU.

The record

CVE
CVE-2026-55831
Published
Jul 20, 2026
Updated
Jul 20, 2026
Vendor
The Netty Project
Product
Netty
Classifications
CWE-400, CWE-770, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 20, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 20, 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=>= 4.1.0.Final, < 4.1.136.Final
  2. Affected versionversion=>= 4.2.0.Final, < 4.2.16.Final

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Netty Project · Nettyversion=>= 4.1.0.Final, < 4.1.136.Final; version=>= 4.2.0.Final, < 4.2.16.Final

Published CVSS scores

7.5GitHub, Inc.CVSS: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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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
CWE-770Allocation of Resources Without Limits or Throttling
T1190Exploit Public-Facing Application

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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