CVE-2026-34084
CVE-2026-34084 is a remote code execution vulnerability in phpoffice/phpspreadsheet. O3 Security confirms whether CVE-2026-34084 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
PhpSpreadsheet SSRF and RCE via PHP stream wrappers in IOFactory::load
Real-World Exposure
phpoffice/phpspreadsheet🐘phpoffice/phpspreadsheet🐘phpoffice/phpspreadsheet🐘phpoffice/phpspreadsheet🐘phpoffice/phpspreadsheetReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
PhpSpreadsheet is a library for reading and writing spreadsheet files. In versions 1.30.2 and earlier, 2.0.0 through 2.1.14, 2.2.0 through 2.4.3, 3.3.0 through 3.10.3, and 4.0.0 through 5.5.0, when the filename argument to IOFactory::load() is user-controlled, an attacker can supply a PHP stream wrapper path (such as phar://, ftp://, or ssh2.sftp://) that passes the is_file() check in File::assertFile(). The phar:// wrapper triggers deserialization of the PHAR metadata, which can lead to remote code execution if a suitable gadget chain is available in the application. The ftp:// and ssh2.sftp:// wrappers can be used for server-side request forgery. This issue has been fixed in versions 1.30.3, 2.1.15, 2.4.4, 3.10.4, and 5.6.0.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | phpoffice/phpspreadsheet | ≥ 4.0.0&&< 5.6.0 | 5.6.0 |
| 🐘Packagist | phpoffice/phpspreadsheet | ≥ 3.3.0&&< 3.10.4 | 3.10.4 |
| 🐘Packagist | phpoffice/phpspreadsheet | ≥ 2.2.0&&< 2.4.4 | 2.4.4 |
| 🐘Packagist | phpoffice/phpspreadsheet | ≥ 2.0.0&&< 2.1.15 | 2.1.15 |
| 🐘Packagist | phpoffice/phpspreadsheet | all versions | 1.30.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for phpoffice/phpspreadsheet. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update phpoffice/phpspreadsheet to 5.6.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34084 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-34084 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-34084. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-34084 in your dependencies?
O3 detects CVE-2026-34084 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.