What’s Vulnerable › Vulnerabilities

CVE-2026-108357: PhpSpreadsheet: XmlScanner Bypass via Double-Encoded unentity() TOCTOU Allows XXE and Denial of Service

• Severity: high (CVSS 8.8 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-22 · updated 2026-10-23
• Weakness: CWE-611

Description

PhpSpreadsheet is a pure PHP library for reading and writing spreadsheet files. From 3.3.0 until 3.10.8 and 5.10.0, Reader\Xml passes stored SpreadsheetML XML through XmlScanner::scan in Xml::canRead and Xml::trySimpleXMLLoadStringPrivate, while Xml::unentity decodes numeric entities only after each DOCTYPE pattern check. A double-encoded less-than character is reduced by the first callback to another encoded character and by the second callback to a literal less-than sign, so SimpleXML receives an unchecked DOCTYPE and entity declaration. Processing attacker-controlled SpreadsheetML XML can cause entity-expansion denial of service 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 3.10.8 and 5.10.0.

Affected products

• PHPOffice PhpSpreadsheet: from 3.3.0, < 3.10.8; from 4.0.0, < 5.10.0

References

• https://github.com/PHPOffice/PhpSpreadsheet/commit/89f455c133e1a7e2d4abfadc43ce29eb7450d781
• https://github.com/PHPOffice/PhpSpreadsheet/commit/980b5c294493856f1a25754f1e8a1d2185b93738
• https://github.com/PHPOffice/PhpSpreadsheet/releases/tag/3.10.8
• https://github.com/PHPOffice/PhpSpreadsheet/releases/tag/5.10.0
• https://github.com/PHPOffice/PhpSpreadsheet/security/advisories/GHSA-rxj4-h86g-25gc

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