GHSA-XH5M-36R6-47M3 PHPSpreadsheet: XLS/OLE sector-chain self-loop causes memory exhaustion

Summary PhpSpreadsheet's OLE reader follows sector chains from attacker-controlled XLS/OLE metadata without detecting cycles or enforcing a maximum chain length. A tiny malformed .xls/OLE file can set the small-block depot sector chain to point back to itself. During normal XLS detection,...