CVE-2026-42581

Netty: HTTP/1.0 TE+CL Coexistence Bypasses Smuggling Sanitization

Published May 13, 2026 CVSS 3.1 · 5.8 Medium EPSS < 1% KEV · Not listed
Description
Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, HttpObjectDecoder strips a conflicting Content-Length header when a request carries both Transfer-Encoding: chunked and Content-Length, but only for HTTP/1.1 messages. The guard is absent for HTTP/1.0. An attacker that sends an HTTP/1.0 request with both headers causes Netty to decode the body as chunked while leaving Content-Length intact in the forwarded HttpMessage. Any downstream proxy or handler that trusts Content-Length over Transfer-Encoding will disagree on message boundaries, enabling request smuggling. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.

Remediation

No solution or workaround provided in the CVE record

Tracking

Sign in to view the affected projects.

Advisories

Source ID Title
Github GHSA Github GHSA GHSA-xxqh-mfjm-7mv9 Netty HTTP/1.0 TE+CL Coexistence Bypasses Smuggling Sanitization
Ubuntu USN Ubuntu USN USN-8401-1 Netty vulnerabilities
History
Type Values Removed Values Added
CPEs cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:*
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Netty
Netty netty
Vendors & Products Netty
Netty netty
Type Values Removed Values Added
Description Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, HttpObjectDecoder strips a conflicting Content-Length header when a request carries both Transfer-Encoding: chunked and Content-Length, but only for HTTP/1.1 messages. The guard is absent for HTTP/1.0. An attacker that sends an HTTP/1.0 request with both headers causes Netty to decode the body as chunked while leaving Content-Length intact in the forwarded HttpMessage. Any downstream proxy or handler that trusts Content-Length over Transfer-Encoding will disagree on message boundaries, enabling request smuggling. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.
Title Netty: HTTP/1.0 TE+CL Coexistence Bypasses Smuggling Sanitization
Weaknesses CWE-444
References
Metrics cvssV3_1

{'score': 5.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Sep 18, 2026, 12:04 PM
Reserved
Apr 28, 2026, 5:26 PM
Status
Modified
Published
May 13, 2026, 7:17 PM
Modified
Nov 11, 2026, 8:10 PM
Severity
Important
Public date
May 13, 2026, 5:54 PM