PhpSpreadsheet: XmlScanner Bypass via ISO-2022 Escape Sequences Allows XXE and Denial of Service

Overview

PhpSpreadsheet is a pure PHP library for reading and writing spreadsheet files. Prior to 1.30.7, 2.1.19, 2.4.8, 3.10.8, and 5.10.0, XmlScanner::scan in src/PhpSpreadsheet/Reader/Security/XmlScanner.php uses a DOCTYPE detection pattern that accounts for NUL-byte interleaving but not ISO-2022 escape sequences in XLSX XML parts. The escape sequences prevent the scanner from matching the declaration, and XML charset normalization then removes the escape bytes before parsing, exposing a valid DOCTYPE and entity definitions. Processing an attacker-controlled XLSX can therefore cause entity-expansion denial of service on supported PHP versions and can permit local file access or SSRF on PHP before 8.0 or when LIBXML_NOENT is enabled. This issue is fixed in versions 1.30.7, 2.1.19, 2.4.8, 3.10.8, and 5.10.0.

Affected

• PhpSpreadsheet < 1.30.7
• PhpSpreadsheet >= 2.0.0, < 2.1.19
• PhpSpreadsheet >= 2.2.0, < 2.4.8
• PhpSpreadsheet >= 3.3.0, < 3.10.8
• PhpSpreadsheet >= 4.0.0, < 5.10.0

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.