CVE-2026-42587Network attack vector

Unauthenticated memory exhaustion via unenforced decompression limits

Published May 13, 2026 · Updated May 13, 2026

Denial of service in Netty before 4.1.133.Final or 4.2.13.Final allows remote attackers to exhaust memory via compressed HTTP requests. HttpContentDecompressor and DelegatingDecompressorFrameListener fail to pass maxAllocation to Brotli, Zstandard, and Snappy decoders, so decompressed output grows without the configured cap. Exploitation requires a Netty server that enables decompression and relies on maxAllocation; one crafted request can trigger an out-of-memory service crash.

CVSS severity7.5
High
EPSS probability0.99%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Netty before 4.1.133.Final or 4.2.13.Final allows remote attackers to exhaust memory via compressed HTTP requests. HttpContentDecompressor and DelegatingDecompressorFrameListener fail to pass maxAllocation to Brotli, Zstandard, and Snappy decoders, so decompressed output grows without the configured cap. Exploitation requires a Netty server that enables decompression and relies on maxAllocation; one crafted request can trigger an out-of-memory service crash.

The record

CVE
CVE-2026-42587
Published
May 13, 2026
Updated
May 13, 2026
Vendor
The Netty Project
Product
netty-codec-http2
Classifications
CWE-400, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 13, 2026CVE publishedPublication date reported by the CVE source.
  2. May 13, 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=< 4.1.133.Final
  2. Affected versionversion=>= 4.2.0.Alpha1, < 4.2.13.Final

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Netty Project · netty-codec-http2version=< 4.1.133.Final; version=>= 4.2.0.Alpha1, < 4.2.13.Final
The Netty Project · Nettyversion=< 4.1.133.Final; version=>= 4.2.0.Alpha1, < 4.2.13.Final
The Netty Project · netty-codec-httpversion=< 4.1.133.Final; version=>= 4.2.0.Alpha1, < 4.2.13.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 exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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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