CVE-2026-59933

PhpSpreadsheet is affected by a memory-exhaustion denial-of-service in the OLERead::read() path when parsing attacker-controlled XLS/OLE metadata. The vulnerability stems from an unguarded sector-chain walk in the OLE reader that can loop indefinitely (self-loop in small-block depot/sector chains...

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,...

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,...