FTP server crashes with `CoderMalfunctionError: IllegalArgumentException`.

What The Problem Is

Exception

• App Name: Amaze File Manager
• Package: com.amaze.filemanager
• Version: 3.10
• User Action: UI Error
• Request: Application crash
• OS: Linux Android 14 - 34
• Device: FP5
• Model: FP5
• Product: FP5

Crash log

java.nio.charset.CoderMalfunctionError: java.lang.IllegalArgumentException: newPosition > limit: (55 > 37)
	at java.nio.charset.CharsetEncoder.encode(CharsetEncoder.java:624)
	at org.apache.mina.core.buffer.AbstractIoBuffer.putString(AbstractIoBuffer.java:1811)
	at org.apache.ftpserver.listener.nio.FtpResponseEncoder.encode(FtpResponseEncoder.java:49)
	at org.apache.mina.filter.codec.ProtocolCodecFilter.filterWrite(ProtocolCodecFilter.java:299)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain.callPreviousFilterWrite(DefaultIoFilterChain.java:629)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain.access$1500(DefaultIoFilterChain.java:48)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain$EntryImpl$1.filterWrite(DefaultIoFilterChain.java:957)
	at org.apache.mina.core.filterchain.IoFilterEvent.fire(IoFilterEvent.java:84)
	at org.apache.mina.filter.logging.MdcInjectionFilter.filter(MdcInjectionFilter.java:135)
	at org.apache.mina.filter.util.CommonEventFilter.filterWrite(CommonEventFilter.java:80)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain.callPreviousFilterWrite(DefaultIoFilterChain.java:629)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain.access$1500(DefaultIoFilterChain.java:48)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain$EntryImpl$1.filterWrite(DefaultIoFilterChain.java:957)
	at org.apache.mina.core.filterchain.IoFilterAdapter.filterWrite(IoFilterAdapter.java:123)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain.callPreviousFilterWrite(DefaultIoFilterChain.java:629)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain.access$1500(DefaultIoFilterChain.java:48)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain$EntryImpl$1.filterWrite(DefaultIoFilterChain.java:957)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain$TailFilter.filterWrite(DefaultIoFilterChain.java:881)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain.callPreviousFilterWrite(DefaultIoFilterChain.java:629)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain.fireFilterWrite(DefaultIoFilterChain.java:622)
	at org.apache.mina.core.session.AbstractIoSession.write(AbstractIoSession.java:574)
	at org.apache.mina.core.session.AbstractIoSession.write(AbstractIoSession.java:519)
	at org.apache.ftpserver.impl.FtpIoSession.write(FtpIoSession.java:530)
	at org.apache.ftpserver.command.impl.CWD.execute(CWD.java:79)
	at org.apache.ftpserver.impl.DefaultFtpHandler.messageReceived(DefaultFtpHandler.java:211)
	at org.apache.ftpserver.listener.nio.FtpHandlerAdapter.messageReceived(FtpHandlerAdapter.java:62)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain$TailFilter.messageReceived(DefaultIoFilterChain.java:858)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain.callNextMessageReceived(DefaultIoFilterChain.java:542)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain.access$1300(DefaultIoFilterChain.java:48)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain$EntryImpl$1.messageReceived(DefaultIoFilterChain.java:947)
	at org.apache.ftpserver.listener.nio.FtpLoggingFilter.messageReceived(FtpLoggingFilter.java:85)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain.callNextMessageReceived(DefaultIoFilterChain.java:542)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain.access$1300(DefaultIoFilterChain.java:48)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain$EntryImpl$1.messageReceived(DefaultIoFilterChain.java:947)
	at org.apache.mina.core.filterchain.IoFilterEvent.fire(IoFilterEvent.java:74)
	at org.apache.mina.filter.logging.MdcInjectionFilter.filter(MdcInjectionFilter.java:135)
	at org.apache.mina.filter.util.CommonEventFilter.messageReceived(CommonEventFilter.java:70)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain.callNextMessageReceived(DefaultIoFilterChain.java:542)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain.access$1300(DefaultIoFilterChain.java:48)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain$EntryImpl$1.messageReceived(DefaultIoFilterChain.java:947)
	at org.apache.mina.filter.codec.ProtocolCodecFilter$ProtocolDecoderOutputImpl.flush(ProtocolCodecFilter.java:398)
	at org.apache.mina.filter.codec.ProtocolCodecFilter.messageReceived(ProtocolCodecFilter.java:234)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain.callNextMessageReceived(DefaultIoFilterChain.java:542)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain.access$1300(DefaultIoFilterChain.java:48)
	at org.apache.mina.core.filterchain.DefaultIoFilterChain$EntryImpl$1.messageReceived(DefaultIoFilterChain.java:947)
	at org.apache.mina.core.filterchain.IoFilterEvent.fire(IoFilterEvent.java:74)
	at org.apache.mina.core.session.IoEvent.run(IoEvent.java:63)
	at org.apache.mina.filter.executor.OrderedThreadPoolExecutor$Worker.runTask(OrderedThreadPoolExecutor.java:770)
	at org.apache.mina.filter.executor.OrderedThreadPoolExecutor$Worker.runTasks(OrderedThreadPoolExecutor.java:762)
	at org.apache.mina.filter.executor.OrderedThreadPoolExecutor$Worker.run(OrderedThreadPoolExecutor.java:704)
	at java.lang.Thread.run(Thread.java:1012)
Caused by: java.lang.IllegalArgumentException: newPosition > limit: (55 > 37)
	at java.nio.Buffer.createPositionException(Buffer.java:353)
	at java.nio.Buffer.position(Buffer.java:328)
	at java.nio.CharBuffer.position(CharBuffer.java:1651)
	at com.android.icu.charset.CharsetEncoderICU.setPosition(CharsetEncoderICU.java:251)
	at com.android.icu.charset.CharsetEncoderICU.encodeLoop(CharsetEncoderICU.java:189)
	at java.nio.charset.CharsetEncoder.encode(CharsetEncoder.java:622)
	... 50 more

How To Reproduce

1. Accessed “FTP Server” (from the navigation pane).

2. Disabled “Secure Connection” (because FTPS isn't RFC-standard). ^1

3. Connected via dolphin-25.04.0-3.fc42.x86_64, augmented with kio-ftps-0.2-32.fc42.x86_64:

   Name            : kio-ftps
   Epoch           : 0
   Version         : 0.2
   Release         : 32.fc42
   Architecture    : x86_64
   Installed size  : 194.0 KiB
   Source          : kio-ftps-0.2-32.fc42.src.rpm
   From repository : <unknown>
   URL             : http://kasablanca.berlios.de/kio-ftps/
   Description     : An ftps KIO slave for KDE, based on rfc4217.
   Vendor          : Fedora Project
   

   I connected to it from both my client, and a VM running on that client.

Expected behavior

It shouldn't crash.

Screenshots

My Environment

1. The Hardware

   [ro.product.brand]: [Fairphone]
   [ro.build.product]: [FP5]
   

2. The OS

   [ro.build.version.release]: [14]
   [ro.build.display.id]: [FP5.UT2M.B.113.20250319]
   

3. Whether Rooted

   No.

4. The Version Of The Application

   sourcePackage=com.amaze.filemanager
   versionName=3.10
   

Start with the FTP Server entry point and trace the reported CWD path through FtpIoSession.write and FtpResponseEncoder.encode. Reproduce the crash using the listed Android and Dolphin/kio-ftps setup, then verify that the FTP server no longer crashes during that operation.