CVE-2026-50020Public exploitNetwork attack vector

Request smuggling via skipped leading control bytes

Published Jun 12, 2026 · Updated Jun 12, 2026

HTTP request smuggling in Netty before 4.1.135.Final and 4.2.0.Final through 4.2.14.Final allows remote attackers to alter request routing. HttpObjectDecoder's LineParser.skipControlChars advances the reader index past every ISO control or whitespace byte before parsing the request line instead of accepting only leading CRLF pairs. Exploitation requires a pipelined or multiplexed deployment whose front end interprets those bytes differently, creating request-boundary confusion and enabling attacker-supplied requests to reach unintended handlers.

CVSS severity5.3
Medium
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

HTTP request smuggling in Netty before 4.1.135.Final and 4.2.0.Final through 4.2.14.Final allows remote attackers to alter request routing. HttpObjectDecoder's LineParser.skipControlChars advances the reader index past every ISO control or whitespace byte before parsing the request line instead of accepting only leading CRLF pairs. Exploitation requires a pipelined or multiplexed deployment whose front end interprets those bytes differently, creating request-boundary confusion and enabling attacker-supplied requests to reach unintended handlers.

The record

CVE
CVE-2026-50020
Published
Jun 12, 2026
Updated
Jun 12, 2026
Vendor
The Netty Project
Product
Netty
Classifications
CWE-444, CAPEC-33, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 12, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 12, 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=< 4.1.135.Final
  2. Affected versionversion=>= 4.2.0.Final, < 4.2.15.Final

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Netty Project · Nettyversion=< 4.1.135.Final; version=>= 4.2.0.Final, < 4.2.15.Final

Published CVSS scores

5.3GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

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-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
CAPEC-33HTTP Request Smuggling
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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