CVE-2026-50020: Netty

Medium severity, CVSS 5.3. EPSS: 0.4% chance of exploitation in the next 30 days.

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.

Affected products

• Netty Netty: before 4.1.135 (fixed in 4.1.135); from 4.2.0, before 4.2.15 (fixed in 4.2.15)

Published 2026-06-12. Last modified 2026-06-17.