CVE-2026-59899: Netty

High severity, CVSS 7.5. EPSS: 0.6% chance of exploitation in the next 30 days.

Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, `HttpContentEncoder` (the superclass of the production handler `HttpContentCompressor`) maintains a per-channel `ArrayDeque<CharSequence>` named `acceptEncodingQueue` that accumulates attacker-controlled data without any size limit. The queue is filled on the I/O thread for every inbound HTTP request and drained only when the application later writes a non-1xx response. This creates a resource exhaustion vulnerability when an attacker exploits HTTP/1.1 pipelining to flood the connection with requests faster than the application produces responses. This issue has been fixed in versions 4.1.136.Final and 4.2.16.Final.

Affected products

• Netty Netty: before 4.1.136 (fixed in 4.1.136); from 4.2.0, before 4.2.16 (fixed in 4.2.16)

Published 2026-07-29. Last modified 2026-08-06.