CVE-2026-108358 PhpSpreadsheet: XmlScanner Bypass via ISO-2022 Escape Sequences Allows XXE and Denial of Service

What is CVE-2026-108358?

CVE-2026-108358 is a high-severity vulnerability in PHPOffice PhpSpreadsheet, published on 22 Oct 2026.

Official description

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.

Weakness: CWE-776, CWE-611

Which versions are affected by CVE-2026-108358?

10 open source packages ship an affected version, including phpoffice/phpspreadsheet.

How do I fix CVE-2026-108358?

Upgrade phpoffice/phpspreadsheet to a fixed version for your release line: 1.30.7, 2.1.19, 2.4.8 or 3.10.8.

Is CVE-2026-108358 being exploited?

There is no known exploitation of CVE-2026-108358 in the wild and no public exploit code.

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as CLSA-2026-1793283095, GHSA-3x94-m842-937c.