IllegalReferenceCountException while reading the data from ByteBuf

Bug Description

We have a Spring Cloud Gateway Application which uses Netty as a server to process request/response. We see a spike of IllegalReferenceCountException happening on a particular TCP connection, not on any other Connections. Traffic on other connection work absolutely fine.

Below is the complete stack trace:

io.netty.util.IllegalReferenceCountException: refCnt: 0 errorCause: refCnt: 0 extended errorStackTrace: io.netty.buffer.AbstractByteBuf.ensureAccessible(AbstractByteBuf.java:1454),io.netty.buffer.AbstractByteBuf.checkNewCapacity(AbstractByteBuf.java:1432),io.netty.buffer.PooledByteBuf.capacity(PooledByteBuf.java:105),io.netty.buffer.AbstractByteBuf.ensureWritable0(AbstractByteBuf.java:305),io.netty.buffer.AbstractByteBuf.ensureWritable(AbstractByteBuf.java:280),io.netty.buffer.AbstractByteBuf.writeBytes(AbstractByteBuf.java:1103),io.netty.handler.codec.ByteToMessageDecoder$1.cumulate(ByteToMessageDecoder.java:105),io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:288),io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:444),io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420), errorStackTrace: io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:294),io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:444),io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420),io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412),io.netty.channel.ChannelInboundHandlerAdapter.channelRead(ChannelInboundHandlerAdapter.java:93),ocpm.cne.gateway.util.ConnectionCountHandler.channelRead(ConnectionCountHandler.java:60),io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:444),io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420),io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412),io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410)

We would some guidance to understand what could be the reason that it only happens on one connection , while requests on other connections seems to work fine.

Netty version

4.1.109.Final

JVM version (e.g. java -version)

Java 17

The report identifies Netty entry points including ByteToMessageDecoder.channelRead, AbstractByteBuf.ensureAccessible, and the application's ConnectionCountHandler.channelRead, but names no repository file or test. Start by tracing buffer ownership through those stack frames and obtain a reproducible case for the affected connection; done requires identifying a confirmed cause and a test or diagnostic that distinguishes it from normal connections.