Spring CoExchangeFilterFunction introduces potential memory leak if coroutine is cancelled

We are seeing leak logs similar to the below on a regular basis in a production application which uses a number of WebClient filters implemented with CoExchangeFilterFunction.

Example application reproducing the issue can be found here.

Example output:

LEAK: ByteBuf.release() was not called before it's garbage-collected. See https://netty.io/wiki/reference-counted-objects.html for more information.
Recent access records: 
#1:
    io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:300)
    io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:251)
    io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:442)
    io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
    io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
    io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1357)
    io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:440)
    io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
    io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:868)
    io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:166)
    io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:788)
    io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:724)
    io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:650)
    io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:562)
    io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997)
    io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
    io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
    java.base/java.lang.Thread.run(Thread.java:1583)
#2:
    io.netty.buffer.AdvancedLeakAwareByteBuf.indexOf(AdvancedLeakAwareByteBuf.java:647)
    io.netty.handler.codec.http.HttpObjectDecoder$HeaderParser.parse(HttpObjectDecoder.java:1161)
    io.netty.handler.codec.http.HttpObjectDecoder.readHeaders(HttpObjectDecoder.java:726)
    io.netty.handler.codec.http.HttpObjectDecoder.decode(HttpObjectDecoder.java:362)
    io.netty.handler.codec.http.HttpClientCodec$Decoder.decode(HttpClientCodec.java:320)
    io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:530)
    io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:469)
    io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:290)
    io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:251)
    io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:442)
    io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
    io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
    io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1357)
    io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:440)
    io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
    io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:868)
    io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:166)
    io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:788)
    io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:724)
    io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:650)
    io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:562)
    io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997)
    io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
    io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
    java.base/java.lang.Thread.run(Thread.java:1583)
#3:
    io.netty.buffer.AdvancedLeakAwareByteBuf.forEachByte(AdvancedLeakAwareByteBuf.java:677)
    io.netty.handler.codec.http.HttpObjectDecoder$LineParser.skipControlChars(HttpObjectDecoder.java:1229)
    io.netty.handler.codec.http.HttpObjectDecoder$LineParser.parse(HttpObjectDecoder.java:1220)
    io.netty.handler.codec.http.HttpObjectDecoder.decode(HttpObjectDecoder.java:347)
    io.netty.handler.codec.http.HttpClientCodec$Decoder.decode(HttpClientCodec.java:320)
    io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:530)
    io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:469)
    io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:290)
    io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:251)
    io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:442)
    io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
    io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
    io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1357)
    io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:440)
    io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
    io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:868)
    io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:166)
    io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:788)
    io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:724)
    io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:650)
    io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:562)
    io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997)
    io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
    io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
    java.base/java.lang.Thread.run(Thread.java:1583)
#4:
    Hint: 'reactor.left.httpCodec' will handle the message from this point.
    io.netty.channel.DefaultChannelPipeline.touch(DefaultChannelPipeline.java:115)
    io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:417)
    io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
    io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1357)
    io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:440)
    io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
    io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:868)
    io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:166)
    io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:788)
    io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:724)
    io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:650)
    io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:562)
    io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997)
    io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
    io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
    java.base/java.lang.Thread.run(Thread.java:1583)
#5:
    Hint: 'DefaultChannelPipeline$HeadContext#0' will handle the message from this point.
    io.netty.channel.DefaultChannelPipeline.touch(DefaultChannelPipeline.java:115)
    io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:417)
    io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:868)
    io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:166)
    io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:788)
    io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:724)
    io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:650)
    io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:562)
    io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997)
    io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
    io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
    java.base/java.lang.Thread.run(Thread.java:1583)
#6:
    io.netty.buffer.AdvancedLeakAwareByteBuf.writeBytes(AdvancedLeakAwareByteBuf.java:635)
    io.netty.channel.socket.nio.NioSocketChannel.doReadBytes(NioSocketChannel.java:356)
    io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:151)
    io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:788)
    io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:724)
    io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:650)
    io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:562)
    io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997)
    io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
    io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
    java.base/java.lang.Thread.run(Thread.java:1583)
Created at:
    io.netty.buffer.PooledByteBufAllocator.newDirectBuffer(PooledByteBufAllocator.java:410)
    io.netty.buffer.AbstractByteBufAllocator.directBuffer(AbstractByteBufAllocator.java:188)
    io.netty.buffer.AbstractByteBufAllocator.directBuffer(AbstractByteBufAllocator.java:179)
    io.netty.buffer.AbstractByteBufAllocator.ioBuffer(AbstractByteBufAllocator.java:140)
    io.netty.channel.DefaultMaxMessagesRecvByteBufAllocator$MaxMessageHandle.allocate(DefaultMaxMessagesRecvByteBufAllocator.java:120)
    io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:150)
    io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:788)
    io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:724)
    io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:650)
    io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:562)
    io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997)
    io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
    io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
    java.base/java.lang.Thread.run(Thread.java:1583)
: 8 leak records were discarded because the leak record count is targeted to 4. Use system property io.netty.leakDetection.targetRecords to increase the limit.