CVE-2026-50020 | Netty's HttpObjectDecoder skips arbitrary initial control characters when only initial CRLF characters are permitted

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.

Published: 2026-06-12 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-50020 is rated Low Risk (26.2/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.23%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-50020

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.04% 0.23% +0.19%
2 2026-06-12 — 0.04% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-50020

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 1.4 [email protected]

Weakness enumeration for CVE-2026-50020

GitHub Security Advisory for CVE-2026-50020

GHSA-hvcg-qmg6-jm4c · Severity: medium · Ecosystem: maven — Netty: HttpObjectDecoder skips arbitrary initial control characters when only initial CRLF characters are permitted

OS Trackers for CVE-2026-50020

vendor priority summary link
debian not yet assigned CVE-2026-50020 not yet assigned priority: Debian including 1 source packages (netty), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): open 5. https://security-tracker.debian.org/tracker/CVE-2026-50020
redhat medium — https://access.redhat.com/security/cve/CVE-2026-50020
suse medium — https://www.suse.com/security/cve/CVE-2026-50020/
ubuntu medium CVE-2026-50020 medium priority: Ubuntu including 1 source packages (netty), 8 status rows across 8 suites (bionic, focal, jammy, noble, questing, resolute, trusty, upstream): needs-triage 8. https://ubuntu.com/security/CVE-2026-50020

Affected software / configurations for CVE-2026-50020

Vendor Product Version Raw CPE
netty netty < 4.1.135 cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:*
netty netty >= 4.2.0, < 4.2.15 cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:*

References for CVE-2026-50020

cvelogic Threat Intelligence