CVE-2026-55833Public exploitNetwork attack vector

Pre-authentication service interruption via unbounded SPDY inflation

Published Jul 20, 2026 · Updated Jul 20, 2026

Resource exhaustion in Netty 4.1 before 4.1.136.Final and 4.2 before 4.2.16.Final allows remote attackers to interrupt services via SPDY. SpdyFrameCodec continues inflating a zlib-compressed HEADERS block after its raw parser exceeds maxHeaderSize and marks the frame truncated. A reachable SPDY pipeline is required; one small block can force disproportionate CPU and allocation work without exposing or altering data.

CVSS severity7.5
High
EPSS probability0.42%
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 4.1 before 4.1.136.Final and 4.2 before 4.2.16.Final allows remote attackers to interrupt services via SPDY. SpdyFrameCodec continues inflating a zlib-compressed HEADERS block after its raw parser exceeds maxHeaderSize and marks the frame truncated. A reachable SPDY pipeline is required; one small block can force disproportionate CPU and allocation work without exposing or altering data.

The record

CVE
CVE-2026-55833
Published
Jul 20, 2026
Updated
Jul 20, 2026
Vendor
The Netty Project
Product
Netty
Classifications
CWE-400, T1499.004
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

7.5GitHubCVSS: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.

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
T1499.004Endpoint Denial of Service: Application or System Exploitation

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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