PhpSpreadsheet XmlScanner bypass leads to XXE
Vulnerability Description
PhpSpreadsheet is a PHP library for reading and writing spreadsheet files. The XmlScanner class has a scan method which should prevent XXE attacks. However, prior to versions 1.9.4, 2.1.3, 2.3.2, and 3.4.0, the regexes used in the `scan` method and the findCharSet method can be bypassed by using UCS-4 and encoding guessing. An attacker can bypass the sanitizer and achieve an XML external entity attack. Versions 1.9.4, 2.1.3, 2.3.2, and 3.4.0 fix the issue.
Impact Analysis
Refer to official advisory for detailed impact metrics.
Remediation
Ensure systems are updated to the latest vendor-supplied patch levels.
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Credits & Attribution
No credits recorded in the NVD database.
References
- https://github.com/PHPOffice/PhpSpreadsheet/security/advisories/GHSA-jw4x-v69f-hh5w
- https://github.com/PHPOffice/PhpSpreadsheet/blob/39fc51309181e82593b06e2fa8e45ef8333a0335/src/PhpSpreadsheet/Reader/Security/XmlScanner.php
- https://owasp.org/www-community/vulnerabilities/XML_External_Entity_(XXE)_Processing
- https://www.w3.org/TR/xml/#sec-guessing-no-ext-info
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