CVE-2026-59933 PhpSpreadsheet: XLS/OLE sector-chain self-loop causes memory exhaustion

PhpSpreadsheet is a pure PHP library for reading and writing spreadsheet files. In versions 4.0.0 through 5.8.0, 3.3.0 through 3.10.6, 2.2.0 through 2.4.6, 2.0.0 through 2.1.17, and all releases up to and including 1.30.5, the OLE reader follows sector chains from attacker-controlled XLS/OLE...

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...

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,...

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,...