Infinite loop on a malformed .xls whose declared stream size exceeds its block chain

[pawlos]

NPOI Version

2.8.0 latest nuget; reproduced on main

File Type

• XLSX
• XLS
• DOCX
• XLSM
• OTHER

Upload the Excel File

hang_readfully.zip

Reproduce Steps

using NPOI.SS.UserModel;

using var fs = File.OpenRead("hang_readfully.xls");
var wb = WorkbookFactory.Create(fs);

Issue Description

A malformed .xls (OLE2 compound file) passed to WorkbookFactory.Create(Stream) can put NPOI into an unterminating loop that pins a CPU core indefinitely. The loop never returns, so a caller cannot recover by catching an exception - the only options are to abandon the thread or kill the process.