CVE-2026-50020
Netty's HttpObjectDecoder skips arbitrary initial control characters when only initial CRLF characters are permitted
Description
Netty is a network application framework for development of protocol servers and clients. Prior to versions 4.1.135.Final and 4.2.15.Final, before reading the first request-line, `HttpObjectDecoder` skips every byte for which `Character.isISOControl(b)` is `true` (0x00–0x1F and 0x7F) as well as all whitespace. RFC 9112 §2.2 only asks servers to ignore empty CRLF lines preceding the request-line — a carefully scoped robustness allowance intended to handle HTTP/1.0 POST workarounds. Silently absorbing NUL bytes, SOH, STX, and other non-CRLF control characters goes significantly beyond this, and can be exploited for request-boundary confusion in pipelined or multiplexed transports where a front-end component treats those bytes differently. Versions 4.1.135.Final and 4.2.15.Final patch the issue.
INFO
Published Date :
June 12, 2026, 4:16 p.m.
Last Modified :
June 15, 2026, 2:31 a.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update Netty to version 4.1.135.Final or later.
- Update Netty to version 4.2.15.Final or later.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-50020.
| URL | Resource |
|---|---|
| https://github.com/netty/netty/releases/tag/netty-4.1.135.Final | Release Notes |
| https://github.com/netty/netty/releases/tag/netty-4.2.15.Final | Release Notes |
| https://github.com/netty/netty/security/advisories/GHSA-hvcg-qmg6-jm4c | Vendor Advisory |
| https://github.com/netty/netty/security/advisories/GHSA-hvcg-qmg6-jm4c | Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-50020 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-50020
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-50020 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-50020 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Jun. 15, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:* versions up to (excluding) 4.1.135 *cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:* versions from (including) 4.2.0 up to (excluding) 4.2.15 Added Reference Type GitHub, Inc.: https://github.com/netty/netty/releases/tag/netty-4.1.135.Final Types: Release Notes Added Reference Type GitHub, Inc.: https://github.com/netty/netty/releases/tag/netty-4.2.15.Final Types: Release Notes Added Reference Type CISA-ADP: https://github.com/netty/netty/security/advisories/GHSA-hvcg-qmg6-jm4c Types: Vendor Advisory Added Reference Type GitHub, Inc.: https://github.com/netty/netty/security/advisories/GHSA-hvcg-qmg6-jm4c Types: Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 12, 2026
Action Type Old Value New Value Added Reference https://github.com/netty/netty/security/advisories/GHSA-hvcg-qmg6-jm4c -
New CVE Received by [email protected]
Jun. 12, 2026
Action Type Old Value New Value Added Description Netty is a network application framework for development of protocol servers and clients. Prior to versions 4.1.135.Final and 4.2.15.Final, before reading the first request-line, `HttpObjectDecoder` skips every byte for which `Character.isISOControl(b)` is `true` (0x00–0x1F and 0x7F) as well as all whitespace. RFC 9112 §2.2 only asks servers to ignore empty CRLF lines preceding the request-line — a carefully scoped robustness allowance intended to handle HTTP/1.0 POST workarounds. Silently absorbing NUL bytes, SOH, STX, and other non-CRLF control characters goes significantly beyond this, and can be exploited for request-boundary confusion in pipelined or multiplexed transports where a front-end component treats those bytes differently. Versions 4.1.135.Final and 4.2.15.Final patch the issue. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N Added CWE CWE-444 Added Reference https://github.com/netty/netty/releases/tag/netty-4.1.135.Final Added Reference https://github.com/netty/netty/releases/tag/netty-4.2.15.Final Added Reference https://github.com/netty/netty/security/advisories/GHSA-hvcg-qmg6-jm4c